1. "Response to: Arsenic as a preservative of dead bodies."
Source: Snow, John. Lancet, 10 November 1838, p. 264 [Letter to Ed.]
To the Editor of the Lancet
Sir:--As the last Number of your Journal contains an article on preserving bodies for dissection, by injecting them with a solution of arsenious acid, you will oblige me by giving publicity to my reasons for believing such a practice to be highly dangerous, as calculated to expose the dissector to breathe an atmosphere contaminated with arsenuretted hydrogen, which is, perhaps the most deadly combination of arsenic. Nearly two years ago I first prepared, at the school in Great Windmill-street, a saturated solution of arsenite of potash, for the injection of a subject, at the suggestion of Dr. Hunter Lane, the lecturer on chemistry there, who had read an account of its effects in a foreign journal. The injection succeeded, producing precisely the effects and appearances described in your quotation; by passing into the veins and diffusing itself everywhere from the permeability of dead tissues, the solution, in a short time, left the arteries empty, so as to admit the usual red injection. Two or three more bodies were subsequently injected, and during the dissection of one of them, one of the pupils suffered severely from pain in the stomach and bowels, vomiting, and purging.
In the summer of 1837, I injected another body, and dissected it, with five of my fellow students, during the very hot weather of, I think, August. Decomposition was retarded considerably, but there was only one of us who did not suffer more or less indisposition, principally bowel complaints: and the subject gave out a peculiar odour, which I suspected arose from the arsenic rising in combination with the volatile products of decomposition. I took some portions of the body, at the end of five or six weeks, and subjected them to a careful examination, and though they had been drenched with the solution, in the first instance, I found no arsenic remaining.
As an experimentum crucis, I some time afterwards placed some animal substances, in a state of decomposition, on a dish, along with solution of arsenite of potash, and also powdered arsenious acid, and placed over them a bell-glass receiver to collect the gases given off, and, at the end of two or three weeks, I added the air contained in the glass to a sufficient quantity of pure hydrogen to make an inflammable mixture, and burnt this as it proceeded from a small jet, holding a piece of glass in the flame, and I procured a small quantity of metallic arsenic. I expressed my conviction that this mode of injection was dangerous, and it was discontinued at the school. I remain, Sir, your obedient servant,
John Snow, M.R.C.S
58, Frith-street, Soho, Nov. 5th, 1838.
Professor Goodeve expressly mentions, in the article, an abstract of which we have given, that no ill effects were experienced by any of the persons engaged in the dissection of bodies injected with a solution of white arsenic.--Ed. L.
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2. Response to: "Action of recti muscles"
Source: Snow, John. London Medical Gazette, 12 January 1839, pp. 559-60 [Letter to Ed.].
To the Editor of the Medical Gazette
Sir,
I beg to offer some observations on the letter of Mr. Lonsdale, in the Medical Gazette of the 15th of this month, on the action of the recti muscles of the abdomen.--I remain, sir,
Your obedient servant,
John Snow, M.R.C.S.
54, Frith Street, Soho
Dec. 29, 1838.
As I am not about to espouse any of the opinions of previous authors, I shall only notice one or two of Mr. Lonsdale's criticisms of these opinions. He says that if different portions of the rectus muscle had separate contractions, there would then be an unequal pressure upon the abdominal viscera. Now this would not be the case for two reasons: first, because the contraction of any part of the muscle would have a tendency to approximate its two ends, and would consequently produce an equal tension throughout the whole length of the muscle; and, secondly, the abdominal viscera move with sufficient freedom on each other to be placed under the laws which govern fluids, consequently any pressure is felt equally through the whole of these viscera. He says also, in answer to Bertin's opinion, that if the blending of the tendinous intersections of this muscle with its sheath were to enable it to assist more completely the action of the other abdominal muscles, these intersections would then be found adhering to the sheath at its posterior part also, for at present they would pull irregularly. Now Mr. Lonsdale must know that the anterior and posterior parts of the sheath of the rectus become intimately blended at the linea semilunaris, before reaching the muscular [559/560] fibres of the oblique; consequently any degree of traction exerted through the anterior part of the sheath would be as equally diffused as through both parts.
Mr. Lonsdale says, that when this muscle contracts, from being in a straight line, it takes on a curved direction backwards towards the spine; and this is not a mistake or a misprint, for it is a necessary part of the theory he advances, and it is exemplified by an engraving. Now for a muscle, extending in a straight line between two fixed points, to take on a curved form, it must become longer instead of contracting; and in the engraving it is actually figured much longer in its so-called contracted state than when relaxed. When the muscle becomes curved in the manner here described, it is not by its own contraction, but it is drawn into this form by the contraction of the transversus and part of the two obliqui muscles; if it contract when retained in this position, it will draw down the sternum and ribs, causing expiration, but still its tendency will be to assume a straight position. The rectus can only compress the abdominal viscera to the extent it does when it becomes a straight line between the pubes and sternum, after being curved forward; if it continue to contract after it has become straight, or when it is held forcibly in a curve, it will then approximate the sternum to the pelvis. The muscles that can retain it in the curved position backward are stated above; and the diaphragm, by pressing on the abdominal viscera, can curve it forward and retain it so.
I will not comment on Mr. Lonsdale's suggestion that the tendinous intersections give the muscle a greater power of contracting since he supports it only by saying, that the opposite cannot be proved.
I do not see any thing important in the absence of any adhesion between the rectus and the posterior part of its sheath. A muscle that has a separate and individual action, is, of necessity, never so connected with surrounding parts as to have its motions prevented. Between the tendinous intersections on its anterior part the muscle is merely united to its sheath by cellular tissue; and at its posterior part, where the tendinous intersections are scarcely seen, it is connected only by cellular tissue in its whole length.
But the structure even of this muscle does not admit of the application of Mr. Lonsdale's theory: it is not, as he states, composed of an anterior half with tendinous intersections and a posterior half without; but, agreeably to the descriptions of Boyer and Cloquet, the fibres arising from intersection are, for the most part, not inserted into the one immediately above, but dip behind it, and are inserted into a tendinous band higher up, so that few of the fibres of this muscle extend its whole length.
To conclude, I do not think these tendinous bands, which are found varying in number and situation in the rectus abdominis muscle, execute any important office; like the cicatrix on the skin which covers this muscle (the umbilicus) and numerous other parts in the body, they are perhaps the remnant of some more early state of organization.
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3. Response to: "Mechanism of respiration"
Source: Snow, John. Lancet, 26 January 1839, pp. 653-55, [Letter to Ed.].
To the Editor of the Lancet
Sir:--As I consider the paper of Mr. Goodman in the Lancet of Dec. 29, on the important subject of the heart's action, to be open to some objections, permit me to make the following observations on it, by giving publicity to which you will much oblige, Sir, your obedient servant,
John Snow M.R.C.S.
54, Frith-street Soho,
Jan. 5, 1839.
After some preliminary observations, Mr. Goodman, speaking of the thorax, says,-- "The outer walls, or bony arch, possess such strength of material, and peculiar convex form, that the pressure of the atmosphere generally understood to be 15 lbs. on every square inch of surface, is firmly and perfectly sustained by this mechanism, and the contained viscera are protected from its influence."
Now, the most delicate structures on the earth bear the pressure of the atmosphere without detriment, so long as it is equal in all directions; a distended bladder, and bubbles blown in soap and water, bear it, because it is equal inside and out; but this is not what Mr. G. means with respect to the thorax, for he says, "the contained viscera are protected from its influence," which they could not be unless the pressure were entirely on the outside. A thorax, 10 inches deep and 30 inches in circumference (not a very large one), has 300 square inches of surface, and would, in this case, have to resist a force of 4500 lbs., or more than two tons; and, in addition, the diaphragm and the parts closing the top of the thorax, would have to resist half as much; this would require thick walls of cast iron instead of mere flesh and bone. The truth is, that with very slight variations the pressure on every part of the thoracic viscera is exactly the same as on the exterior of the chest. The walls of the thorax are moveable and elastic, and are exactly applied to the surface of the lungs in all their changes in size, and the atmosphere that presses on these walls presses them on the lungs; the atmospheric pressure also, on the walls of the abdomen, is communicated by means of the abdominal viscera and diaphragm, without the slightest diminution to the viscera of the thorax; and the atmosphere communicating with the interior of the lungs, balances, between the respirations, exactly the pressure outside ; it makes no difference that the mouth and nostrils be closed, for the pressure of any given volume of air is precisely the same as that by which it has been compressed. The slight variations of which I have spoken are, that during inspiration the pressure in the interior of the chest is a little less, and during expiration a little more, than on the exterior; that this difference is very minute I will prove at the end of this paper.
Immediately after the sentence I have quoted, Mr. Goodman continues:--"Not only does this protecting arch resist the force of external pressure, but it is also capable, to a certain extent, of expanding itself, and producing a partial vacuum within its parietes." The latter part of this sentence is not at variance with fact. Mr. G. continues,--"The diaphragm, or floor of this cavity, is also able to resist the power of atmospheric pressure, although of muscular construction." I need not comment on this, after what I have said above.
The experiment of removing the heart through an opening in the diaphragm, and then inflating the lungs, does not prove that the pericardium is capable of resisting any [653/654] degree of pressure, either from the lungs or the atmosphere, since, when the abdomen was opened, the diaphragm would descend to allow of the distention of the lungs with the greatest ease.
Mr. G. says there is, apparently, no increase in the volume of a muscle to account for its diminution in length; and that he means thickness, or circumference, by volume, and not the entire bulk, is evident from the application he makes of it. Now, he has only to place his hand over the biceps muscle, and contract it, to perceive the opposite of this; and on turning to page 211 of "Baly's Translation of Müller's Physiology," and seeing it there stated that "the primitive fibrils of the muscles of man are five or six times smaller than the red particles of his blood," Mr. G. will, I am sure, at once relinquish his "speculative conclusion, that the primitive muscular fibre is composed of an extremely minute cellular structure of, probably, globular cells, arranged longitudinally in its substance, and for the purpose of receiving and being distended by arterial blood," [etc.]
Further on we find it stated, that "either the anterior walls of the pericardium must give way, and follow the contraction of the ventricles, or a vacuum must take place betwixt the apex of the heart, and the sternum it has now relinquished." Mr. Goodman must have derived this opinion from the speculative conclusion alluded to above, for all previous authors say that the apex of the heart is projected forward against the sternum during the contraction of the ventricles, and that this projection commences with the very beginning of the contraction is evident from the impulse being exactly synchronous with the first sound of the heart, which is caused by the contraction of the ventricles.
With respect to the ingenious experiments with the glass pericardium, it is necessary to observe, firstly, that if the thoracic viscera were defended from atmospheric pressure, as Mr. G. states, then the phenomena he exhibits could not take place, whatever were the structure of the pericardium, since it is by this pressure these phenomena are produced; and secondly, that with those viscera, situated as they are, no vacuum, partial or complete, could exist in the pericardium, unless it were as firm and unyielding as the glass vessel by which Mr. G. has represented it; whereas the pericardium, though a strong fibrous membrane, and capable of resisting solution of its continuity, is not able to retain any particular shape in opposition to any part of the pressure of the atmosphere, which is freely communicated through the diaphragm below and the lungs on each side, and must retain it as accurately applied to the surface of the heart during all its motions, as it keeps the sides of the thorax applied to the surface of the lungs; and the serous coat of the pericardium, reflected over the heart, must glide over the serous lining of the fibrous coat during these motions as freely as the pleura pulmonalis glides over the pleura costalis. Mr. Goodman says, that the impulse of the heart is caused by the pressure of the atmosphere forcing the blood into the auricles, and "causing its apex to strike the posterior surface of the sixth rib, in a similar manner that the piston of a condensing engine is, by the power of the steam, carried with terrific violence through the vacuitous portion of the cylinders."
If the theory of the pericardium given in the paper under consideration were correct, it would be almost impossible for the circulation to continue a moment after the pericardium became adherent all over the surface of the heart; yet Dr. Hope tells us that persons may live for some years after such is the case, and I have examined a heart that was firmly adherent everywhere to the pericardium, whilst the inflammation which caused this adhesion took place some months before the patient's death.
There is one tendency to a vacuum which does assist the circulation of the blood, and to which Mr. G. has not alluded. Dr. Williams tells us that the hand, grasping the heart of a donkey, cannot prevent the expansion of the ventricles when they are contracted; this active expansion, then, must remove, in part, the pressure of the atmosphere and cause the blood to be driven into the ventricles.
Mr. Goodman states that the ventricles propel the sanguineous fluid against the whole pressure of the atmosphere throughout the body, [etc.] Now, the ventricles could do no such thing; and that they have to do no such thing, is evident from what I have said about the thorax; except the deviation that respiration causes, the atmospheric pressure does not interfere, and during expiration the flow of arterial blood from the thorax is assisted and during inspiration retarded, and the extent of this deviation has been measured by M. Magendie, and is given in his lectures in a recent number of the Lancet, where it is also seen that the force of the arterial current in dogs is generally equal to a column of from 70 to 100 millimetres of mercury, which is from three to four inches, or from one-tenth to one-eighth of the pressure of the atmosphere.
One of the conclusions at which Mr. G. arrives from his experiments is, "that there is no necessity at all for muscular fibre in the parietes of the auricles for facilitating or producing the action of the heart." But since anatomists tell us that muscular fibres exist there, we may fairly conclude that they perform some function; and most persons who have experimented on animals [654/655] have seen the auricles contract, and generally before the contractions of the ventricles.
As the remainder of the paper is principally occupied with conclusions from the parts on which I have already commented, I need offer no further remark on it.
It is strange that Müller, in his Physiology, attributes to Sir David Barry this very idea of a vacuum in the pericardium; and it is more strange that he seems to receive this idea and to concur in it. I give the passage from p. 234 of "Baly's Translation:"-- "Sir David Barrv has recently given a new turn to these inquiries, respecting the circulation in the veins. The heart, he says, when distended with blood, completely fills the pericardium; but when it contracts, it no longer occupies the same space, and a partial vacuum ensues. To enable the auricles to fill this vacuum, the blood rushes into them from the great venous trunks. But, Sir D. Barry attributes more importance to the effect of inspiration" [etc.] Now, Sir David Barry's experiments on the pericardium were instituted to show that the partial vacuum which exists in the thorax during inspiration, extends also to the pericardium, and not that there is any special vacuum in the pericardium caused by the contraction of the heart, and he found that when a tube was inserted into the pericardium of an animal, fluid was drawn up into that cavity during inspiration; and the only passage in his book that might lead to an idea that the contraction of the heart at all influences the result, is the following, at page 20:-- "Although the fluid invariably halted, or descended, during expiration, there was an oscillation of the fluid upwards, which seemed independent of respiration, and could not be perceived during inspiration, because then it was confounded with the general motion of the liquid upwards. This third movement was acknowledged by my friend Mr. Bennett."
The real amount of variation that respiration causes in the atmospheric pressure, exerted on the thoracic viscera, I have ascertained by the following simple experiments:--By fitting a glass tube into one of the nostrils, leaving the other nostril open, and dipping the lower end of the tube into mercury, it is found that the mercury rises in the tube during inspiration a very little above its level on the outside, perhaps about a line, and sinks the same depth below its level during expiration; if the tube is dipped in water instead of mercury, the water rises and falls about an inch above and below the surface. If the other nostril be closed, and a powerful act of inspiration made, the tube being dipped in mercury, the mercury will be raised nearly two inches; if dipped in water, that fluid will be raised about two feet; during a powerful expiration the fluids are depressed an equal degree below their level. It is thus evident, that during natural respiration the variation in atmospheric pressure is about one 400th part of the whole pressure; and, in violent respiration, about one-15th of the whole pressure, or one pound on the square inch, can be alternately added to and removed from, the equable pressure. On comparing MM. Magendie and Poiseuille's experiments on the large veins near the thorax in dogs, detailed in the Lancet of Dec. 15th, with these, and turning the millimetres into inches, I find there is reason to believe that there is not much difference between the respiration of dogs and human respiration as regards variation in pressure. I find that in spasmodic expiration, the chest being first expanded, as sneezing, mercury may be depressed for a part of a second, four or five inches below its level; this is best seen by having the mercury in a bent tube, when the rise of the mercury is seen in the other limb. The tube must not be put in the mouth during these experiments, as the act of suction performed by the mouth can raise mercury eight or nine inches, in addition to the act of respiration.
It is evident from these experiments that Sir David Barry much overrated the assistance which respiration gives to the venous circulation; but since M. Magendie has recently put the question in its true light, by experiments on the veins themselves, I need not dilate upon it. I will merely observe, in conclusion, that Sir D. Barry, in explaining the modus operandi of his important apparatus for preventing absorption in poisoned wounds, ought to have said, that in removing the atmospheric pressure from a part, he engages that pressure on the surrounding parts to oppose the absorption; instead of saying, as he does, that atmospheric pressure is the great agent of absorption, which is, therefore, prevented by removing that pressure.
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4. Response to: "On the bands in the recti muscles"
Source: Snow, John. London Medical Gazette 9 February 1839, pp. 719-20 [Letter to Ed.].
To the Editor of the Medical Gazette
Sir,
You will greatly oblige me by allowing a place in your valuable journal to the following observations on the letter of J.C.C., in the Medical Gazette of Saturday last, containing Mr. Mayo's judgment on the subject of my communication in your number for the 12th inst. viz. the action of the recti muscles of the abdomen.--I remain, sir,
Your obedient servant,
John Snow.
54, Frith Street, Soho
Jan. 28, 1839.
Mr. Mayo gives us two uses for the tendinous intersection of the rectus abdominis: first, "that in certain positions of the body the recti describe a curve, and have to maintain or increase that curve while they are in action." The only action a muscle has, is to shorten itself, and in doing so, whilst it is attached at both ends, so far from maintaining or increasing a curve, its tendency evidently must be to become straight; and unless the rectus were retained in the curved form by other muscles, it could never act either on the thorax or pelvis, except when straight. After shewing that this curved form does occur, it is stated that these tendinous intersections "when braced tight by the fibres of the internal oblique, with the tendon of which they cohere, allow the intervening portions to describe arcs of segments of the entire curve, and permit the whole to become concave forwards, while its several parts are shortening, and perhaps straightening." This does not explain the use of those tendinous intersections, for the tendon of the internal oblique, together with those of the external oblique and the transversalis forms a sheath for the rectus, one half of which passes in front of it, and thus when those muscles are in action they not merely permit the whole," but they compel the whole "to become concave forwards," and would do this just as effectually without these intersections as with them.
If it were necessary to add analogical inference to direct proof, I might remark that there are many muscles without tendinous intersections which act whilst they are curved, as the muscles of the spine occasionally, and the transversus abdominis and diaphragm at all times, and that these intersections exist in the rectus of animals in which the muscle never forms a curve towards the viscera.
The other use we are given for these tendinous intersections is, that they enable one portion in length of the muscle to act occasionally without the other. Now since many of the fibres dip behind each intersection, and are continued to another one, so that no intersection divides the whole of the muscle, it is impossible to conceive how one part of the muscle can act without the rest. Mr. Mayo gives us an instance of this particular action, the gymnastic feat of raising the body by the hands, and states that the upper halves of the recti pull "the lower part of the body upwards, as if they drew upon so many belts, which are fixed and girded by the action of the oblique and transverse. The lower [719/720] halves of the recti are at the same time in moderate action." Surely the muscles would raise the lower part of the body more effectually and comfortably by drawing upon the pubes than upon these belts, and I have examined the recti of a man during this feat, and found them as hard as a board throughout their whole length. However, this action is not exerted for the purpose of pulling up the lower part of the body; this is in the same piece with the upper part, and needs no such pulling upwards, and any action between the chest and lower part of the body would no more lessen the weight to be raised by the arms and shoulders, than a person standing in a balance would lessen his weight by lifting up one leg, or pulling at the cord of the scale, or any other maneuver. This action of the recti, in addition to assisting to steady the chest, a measure necessary in all powerful actions of the arms, is exerted to draw the lower part of the body forwards, and make it project beyond the pole, to balance the upper part which is on the other side, and keep the certain gravity of the body on the same perpendicular plane with the pole, that the arms may simply have to raise the weight of the body, without the disadvantage of its being at the further end of a lever; the necessity of which is seen by the impossibility of raising the body without allowing the legs to project under the horizontal pole, or of pulling it up the side of a wall, without touching the wall with the legs or feet.
So far, then, I am fully borne out in repeating the remark with which I closed my last letter, not "denying any use in the arrangement," as J.C.C. states, but saying that "I do not think these tendinous bands execute any important office."
These bands exist, I believe, in the rectus of all animals down to reptiles. Carus says that the frog is without the transverse tendinous ligaments belonging to fishes and salamanders, and the only vestiges of them are in the recti muscles of the abdomen. These transverse tendinous bands in fishes, it should be remembered, correspond in number to the vertebrae, and the bands in the rectus of man are never more numerous than the vertebrae between the chest and pelvis, viz. five.
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5. On distortions of the chest and spine in children from enlargement of the abdomen.
Source: Snow, John. London Med. Gazette, vol. 28, 9 April 1841, pp. 112-116.
By John Snow, M.R.C.S.
(For the London Medical Gazette.)
ead at the Westminster Medical Society on March 13, 1841.
It is not my intention to describe the various deformities to which the chest and spine of children are liable, but only to speak of one or two distortions which arise from enlargement of the abdomen--a cause of deformity which, hitherto, has not, that I can find, been recognised by authors.
I shall relate only one, out of a few cases that I have witnessed, which will serve sufficiently to illustrate the points that I wish to establish.
Aug. 16, 1839.--Hugh Lynch, a twin child, aged two years and five months, has had a double scrotal hernia from birth. He has been ill for the last four months; his mother says much in his present condition. The abdomen is very large and tympanitic; the chest is broad behind, very narrow in front, and flattened at the sides; the sternum projects forwards very much, especially at the lower end. The cartilages of the ribs, instead of passing outwards from the sternum on each side, leave that bone at another angle by no means very obtuse, and pass backwards to meet the osseous part of the ribs at another angle; and the cartilages of the false ribs project laterally from the bony portion, so that the lower part of the chest is much expanded where it unites with the enlarged abdomen. The last of the dorsal and first of the lumbar vertebræ project backwards, whilst the lower lumbar vertebræ project forwards and the sacrum backwards. The child is emaciated and feverish; its bowels are disordered, and its appetite is craving. Its mother feeds it chiefly on potatoes. The breathing is quick, the inspiration being easy, but the expiration difficult, and attended with all effort approaching to a cough; the upper part of the air–passages being closed after each inspiration, and then the air escaping with a slight sound, similar to that which takes place after the breath has been held for the performance of any muscular exertion. During each inspiration the abdomen descends and protrudes, and the cartilages of the ribs are forced inwards on each side of the sternum. During expiration, on the contrary, the abdomen retreats, and the ribs return to their previous situation. There is loud puerile respiratory murmur, and the chest yields a clear sound on percussion at all parts.
To take some Hydrargyrum cum Creta, and be fed in a more rational manner.
Sept. 27th.--The child is more emaciated. His belly is still large, but much less than before. His chest is of the same form, but the cartilages of the true ribs do not fall in so much during inspiration; those of the false ribs, however, are drawn inwards by the diaphragm at each inspiration, and so project towards the lower end of the sternum, whilst a hollow is left just beneath at the scrobiculus cordis. The thorax yields a clear sound on percussion, but there is a mucous rale.
The child died on Oct. 29th.
Examination, seven hours after death--The spine is now pretty straight. Abdomen very much less than formerly, but yet tumid. The chest yields a dull sound on percussion throughout the greater part of its extent, although a few hours before death it sounded clear. On opening the abdomen, the diaphragm, instead of its usual arched form is found to be stretched horizontally across the body, so that it is not so high as the seventh rib. The lungs are healthy in structure, but the whole of the left lung and the lower lobe of the right are collapsed and totally void of air, and gorged with dark fluid blood; the remainder of the right lung is crepitant and healthy. The heart is healthy, but the pericardium contains three or four drachms of serum. Each rib is enlarged into a spongy head at the part where it unites with its cartilage.
The large intestines are distended with flatus, except in portions where they are firmly and preternaturally contracted. The colon is so much lengthened that it crosses the abdomen three or four times. The cœcum is in the usual position, and from this the colon extends to the left side and back again, then passes upward to the stomach, across the abdomen, and down the left side in the usual route to the sigmoid flexure; which flexure extends into the right iliac fossa, and back to the median line, where it unites with the rectum. The remainder of the abdominal viscera were healthy. The head was not examined.
In order to show satisfactorily that this deformity of the chest is caused by the enlargement of the abdomen, I must prove that the space within the thorax is increased by any great distension of the abdomen, and not diminished, as is generally supposed. As the belly increases in size, the false ribs, with their cartilages, are pressed upwards, and approaching to a right angle with the spine; the circumference of the chest is thus increased, and the abdominal muscles, which by drawing down the ribs are the chief agents of expiration, can but ill perform their duty; they are kept on the stretch by the bulging out of the viscera, or whatever they enclose. Moreover, the diaphragm, [113/114] being attached to the base of the chest all around, has its borders drawn further apart by the increased circumference of the thorax, and thus its natural arched form is removed; it approaches to a plane partition, and the chest, so far from being encroached upon by the abdominal cavity in this direction, has its perpendicular length increased.
I may here state I have always observed that the difficulty of breathing arising from enlarged abdomen, whether in human beings or quadrupeds, consisted in obstructed expiration, and not obstructed inspiration when there was no other cause of dyspnea.
The bellies of children are subject to a very much greater proportional enlargement than ever obtains in the adult, and the cartilages and ligaments of the ribs being more flexible and distensible, the expansion of the base of the chest becomes very great; and as the lungs are compelled by the atmospheric pressure to occupy every part of the chest, they must either be preternaturally distended, or the chest must be depressed in some other direction. Now, as the ribs and their cartilages are slender and flexible in children, the latter takes place; the chest becomes depressed laterally, and the sternum projected forwards, whilst a channel is left down each side of the chest where the cartilages unite to the bony portion of the ribs. The action of the diaphragm, which presses down the abdomen, and at the same time draws up the cartilages of the lower ribs, during each inspiration, makes room for more air than the lungs are inclined to receive, and the sides of the chest are pressed further in during each inspiration, and return again during expiration: thus the motion of the ribs becomes the reverse of the natural one. I do not conceive this arises from the mechanical resistance of the lungs, but from the sudden stoppage at the throat to the further access of air, which I have observed to be never absent during this deformity with inverted motion of the ribs. It is made evident by the slight explosive sound when the passage is again opened at each expiration. This check to the further ingress of air is no doubt a voluntary or instinctive effort to avoid the uneasy sensation arising from too great distension of the lungs. I do not think it consists in a closure of the glottis, but in the approximation of the posterior palatine arches, and the pressure of the root of the tongue at the same time against the palate of the mouth: the method by which, as Dzondi has discovered, the breath can be held. It is the office of the serratus magnus and the pectoral muscles to expand the sides of the chest during inspiration, but the diaphragm enlarging the chest more powerfully in another direction, these muscles yield to the atmospheric pressure, and eventually, so far as respiration is concerned, become paralysed.
I have never seen enlargement of the abdomen to great extent in a child under three years of age, that was not accompanied with this deformity of the chest. The degree of deformity is always in proportion to the enlargement; and in observing any individual case, the deformity is found to increase with the increasing size of the abdomen. Even when the enlargement of the belly is not great, there is a tendency to this deformity observable in the slight lateral projection of the cartilages of the false ribs. After the age of three or four years I have not observed this deformity to commence, probably because the ribs become of a strength which prevents it; besides that the abdomen is not so liable to become tumid.
The other deformity, that of the spine, seems to be only an occasional, and not a constant attendant on enlarged abdomen: I think it is in the worst cases that it prevails. It consists in a projecture, frequently an angular one, of the last dorsal, or great lumbar vertebræ, or both. In the case I have just detailed it was accompanied by a secondary projecture of the sacrum; and in another case it was attended with a slight lateral deviation. This projecture of the spine is probably caused by the stretched abdominal muscles and integuments, drawing, by means of the pelvis and chest, on the opposite ends of the spinal column, whilst the increased contents of the abdomen make a resistance in the centre. That this angular projecture of the spine depends on disease of the bodies of the vertebræ in the first instance, we are forbid to suppose, by the fact that the projecture subsides as the abdomen diminishes.
In one child, an angular projecture [114/115] for which the formation of issues had been previously recommended, perfectly disappeared as the child resumed his health, under tonic and alterative medicines, with attention to diet, and bandaging of the abdomen. It most likely depends on partial absorption of the intervertebral substance, or bending of the bodies of the vertebræ at the affected part, and, if continued, might no doubt lead to permanent disease.
Baron Dupuytren, in a paper published in the "Repertoire Géneralé d'Anatomie et de Physiologie," in 1828, described a deformity of the chest of children, which I believe, in many of his cases at least, to be the one of which I am speaking. It occurred in children badly clothed and fed, born of unhealthy parents, and living in damp situations, and was accompanied, in most cases, by enlarged tonsils, requiring sometimes to be extirpated. He said that there was a keel-like projecture of the sternum in front, and a sharp prominence of the spine; that the ribs were not only flattened, but that they were sunk into the chest as if they had been compressed from one side towards the other. This deformity was accompanied with great difficulty of breathing. He did not mention the abdomen, except in his preliminary remarks, to say that there was projecture forwards of the sternum and belly; and he only alluded to it, I think, in one of his illustrative cases, in which, however, he said the belly was five times as large as the chest. In another case he spoke of the width of the chest at the base. He appeared to attribute the deformity to arrest of ossification, and softness of the bones; and recommended some mechanical measures and exercises, in addition to medical treatment, for its cure. He spoke of some cases in new–born infants, which, I think, could not have the same origin as the cases I have seen. The nature of the connection between these deformities and the enlargement of the tonsils, he could not tell.
I have only seen one case since I read Baron Dupuytren's paper, and in this there was no enlargement of the tonsils. I can, however, suppose that the obstruction to inspiration from enlarged tonsils, might cause the ribs of a child to be pressed inwards by the atmosphere, and produce a deformity of this kind.
In the Medical Gazette of January 12th, 1839, is a letter by Mr. Rees, describing the deformity of the chest of which we are treating as occurring in four or five children seen by him at the Tower Hamlets Dispensary. He describes the depression at the line of union between the ribs and their cartilages, producing a channeled appearance external to the sternum on each side; and he likewise describes the inverted action of the ribs in respiration. Mr. Rees does not mention the abdomen, except in the case he relates for illustration, in which he incidentally says it was tumid. He attributed the deformity to chronic pneumonia, which causing the lungs to shrink and become solidified; the ribs are forced in by the atmospheric pressure to occupy the space. We can perceive that shrinking of the lungs might have this effect, but in the cases I have witnessed there was no disease of consequence in the lungs, except in one child that had hooping-cough.
Mr. Amesbury describes this deformity, and the enlargement of the abdomen in connection with it; but he does not speak of them in the relation of cause and effect. He attributes this deformity to weakness of the muscles. He says, "Deformity of the chest, arising from weakness of the muscles, commonly takes place during teething, but may be produced by any complaint that tends to debilitate the system. This distortion usually assumes the form called 'chicken–breast.' In this variety of deformity the chest is usually more or less contracted laterally, the sternum is thrust forward, and the abdomen is preternaturally enlarged. The intercostals muscles act very little in respiration, the breathing being principally abdominal." Together with medical treatment for the improvement of the general health, Mr. Amesbury recommends bandaging the abdomen for the cure of this deformity.
Baron Dupuytren and Mr. Amesbury do not mention the reversed action of the ribs in breathing. Mr. Rees and Mr. Amesbury do not allude to any deformity of the spine; and the projecture to which Baron Dupuytren alludes appears to be one of the whole spine, and not of particular vertebra.
In two or three of the cases I have seen, the inferior extremities became deformed under the weight of the enlarged belly, but it was the joints which yielded, and not the shafts of the bones; and there was only in one case the enlargement of the heads of the bones peculiar to rickets: where rickets exists it may assist to aggravate the deformity, but cannot of itself cause it. A scrofulous diathesis, by predisposing to mesenteric disease, may be considered favourable to the development of these deformities; but in the cases I have seen, I do not remember to have observed enlarged glands, or other decided marks of scrofula. And in the only two cases in which I have had the opportunity of an examination after death, there was no disease of the mesenteric glands, and the enlargement depended chiefly on the elongation and distension of the colon.
I have generally been able to trace the increased size of the belly to improper food, and have found it mostly amongst those infants who, from the poverty or intemperance of their parents, are, after weaning, fed almost entirely on potatoes. I believe the best treatment to consist in alteratives and tonics, with occasional purges, and the careful avoidance of crude and indigestible food. At the same time the abdomen should be firmly bandaged, as recommended by Mr. Amesbury, which measure, whilst it assists to reduce the belly to its natural size, will relieve the breathing by aiding the efforts of expiration; and by pressing the diaphragm upwards, will reduce the capacity of the base of the chest, and thus lessen the cause of the contraction higher up. If this deformity be left to itself, and should not prove fatal, the serratus magnus, and other muscles, may not recover their power of expanding the ribs, or the ribs may have become firm in their abnormal shape, and the deformity may continue, after the enlargement of the abdomen, which gave rise to it, has subsided. I have seen two or three cases of this deformity in grown–up persons, which, so far as I could gather the history, appear to have originated in this manner.
Thus, then, I have endeavoured to establish that enlargement of the abdomen in children leads to deformity of the chest, and occasionally of the spine; and that although the deformity of the chest, or one nearly resembling it, may now and then arise from other causes, yet that this enlargement is of itself sufficient, and will never fail to induce it, if proceeding to any great extent in young children.
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6. On asphyxia, and on the resuscitation of still-born children.
Source: Snow, John. London Med. Gazette, vol. 29, Nov. 5, 1841, pp. 222-227.
By John Snow, M.R.C.S. for the London Medical Gazette, Read at the Westminster Medical Society on October 16, 1841.
Respiration, in a limited sense, signifies the mutual change which takes place between the oxygen of the air and the blood; and this is not strictly a vital process, but only an operation of organic chemistry, since it continues after death as well as before, when the mechanical advantages for access of air remain the same. The celebrated Spallanzani, in his work on Respiration, has shown that snails and other animals, which respire chiefly by the surface of the body, continue after death to absorb to some extent the oxygen of the air, and replace it by carbonic acid until the time when putrefaction commences. When insects are poisoned by prussic acid, they come to life again after a little time, because respiration has been going on by the tracheal tubes without any effort of the animal. We know likewise that venous blood can be changed to that of arterial tint by agitation with air out of the body, producing in the air the same change as respiration.
Respiration seems essential to the life of the whole animal kingdom, and when it is arrested from any cause the state called asphyxia is induced. Asphyxia in the human being, and the higher class of animals, after the fetal circulation is lain aside, presents the following phenomena:--The blood at once ceases to be changed in colour whilst passing through the lungs, and venous blood circulates in the arteries; but in a very little time the blood is refused admission through the capillaries of the lungs, and the circulation is arrested. The blood accumulates in the pulmonary arteries and the right side of the heart, whilst the pulmonary veins and the left side of the heart become empty. The heart continues to act for some time, and would propel the blood through the system if it would pass the lungs. Consciousness and voluntary motion soon cease, generally in from one to three minutes after the stoppage of respiration; convulsive motions and attempts at inspiration supervene, and continue for a short time, but all signs of life soon disappear.
It is a question whether insensibility is occasioned by the circulation of venous blood, or by the stoppage of the circulation. Bichat concluded that venous blood acted as a poison on the nervous centres and animal textures generally, and thus destroyed life, in which view he, no doubt, went rather too far, since no ill effects remain from the circulation of dark blood, if respiration be renewed in time. Dr. Kay and others conclude, from some experiments, that venous blood, although not so good a stimulus to the brain as arterial, yet tends to maintain life; but the ordinary venous blood which they injected was not so utterly deprived of its arterial properties as the blood of an asphyxiated person, which has circulated twice or thrice round the body. They might indeed have spared themselves the trouble of their experiments, if they had but considered that newborn animals in which the foramen ovale and ductus arteriousus are open, that all these, except a few species which are born in a very immature state, with the eyes closed, die when drowned nearly as quickly as adults, although venous blood continues to be sent to the brain and all parts of the system; the action of the heart being the last sign of the heart to disappear. Moreover, Dr. John Reid, of Edinburgh, has lately shown, by direct experiment, that voluntary motion ceases in asphyxia before the force of the circulation is diminished. It is clear, then, that blood which has totally lost its arterial properties, is unable to maintain sensibility or even vitality. The arrest of circulation at the lungs, however, may probably shorten life by some seconds, or even by a minute or two.
It has been a subject of conjecture with physiologists whether the carbonic acid gas produced by respiration is formed in the lungs by direct union of the oxygen of the air with the carbon of the blood, or whether the oxygen is absorbed and dissolved in the arterial blood, and unites with carbon in the capillary circulation of the system, where the blood becomes venous, forming carbonic acid, which is given off in the state of gas into the air-cells of the lungs. The latter theory has been shown to be the correct one by the experiments of Spallanzani, repeated by Dr. Edwards, on respiration in hydrogen gas, and by the experiments of Professor Magnus on the blood. The formation of carbonic acid by respiration is no doubt the chief if not the sole cause of animal heat. The quantity of heat developed just about equals the caloric that would be given out by the union of oxygen and carbon under any other circumstances to form the amount of carbonic acid produced by respiration, and the development of carbonic throughout the animal kingdom bears always a direct proportion to the quantity of carbonic acid evolved. On these considerations respiration has been compared to combustion, and the lungs to a furnace; but as we have seen that the carbonic acid is really produced in the capillary circulation of the system, and only evolved by the lungs, the whole body ought to be compared to the furnace, and the lungs to the draught and chimney department -- a view which better explains the uniform diffusion of warmth throughout the body. It may be asked whether asphyxia is occasioned by want of oxygen in the blood, or by the poisonous effects of the carbonic acid detained in it? The former is the correct view, since asphyxia takes place in nitrogen or hydrogen gas the same as if respiration were stopped, notwithstanding the mechanical process is continued, and the carbonic acid continues to be given off from the lungs.
Several theories have been advanced to account for the arrest of the circulation through the lungs, but that of Dr. Alison is by far the most satisfactory; viz. that the motion of the blood in the capillaries is assisted by the vital attractions connected with the chemical changes which are constantly going on to effect nutrition and secretion; and that consequently, when the supply of oxygen is cut off, and the chemical change of the blood is prevented, the heart of itself is unable to propel the blood through the capillaries of the lungs. This opinion has lately been strengthened by the discovery of Dr. J. Reid, that there is in asphyxia an impediment likewise to the passage of the blood through the capillaries of the greater circulation, when the opposite change would be taking place in the blood if it were not already in a carbonized or venous state.
A consideration of great practical importance in the study of asphyxia is, the influence of the temperature of the medium in which it takes place. Dr. Edwards, of Paris, by a most extensive and beautiful set of experiments, has proved that throughout the animal kingdom asphyxia is much more sudden at a high than at a low or moderate temperature; and that even cold-blooded animals, which will linger for hours deprived of oxygen at a low temperature, will die as quickly as mammalia or birds in water at blood heat: even fishes will die in a few seconds, or at most two minutes, in water at 100° Fahrenheit, that has been deprived of its air by boiling, although this temperature would not injure them with sufficient air. He found that new-born mammiferous animals die most slowly in water at about 60 degrees, which is ordinary cold water, and that they die much more quickly as the water approaches blood heat. Dr. Edwards advises that persons in the state of suspended animation should amongst other measures, be exposed to the cool air: and that the application of heat should be avoided, unless indeed just a momentary application, to endeavour to arouse sensibility. The Royal Humane Society, however, directs the application of warmth in all practicable ways, not only as an auxiliary to artificial respiration, but even to commence with, if the means for the latter are not in readiness; and most authors, I believe, coincide with the views of the Humane Society. Dr. Edwards considers it is by its effects on the nervous system, and through that on the heart, that a high temperature produces its effects. I think that, although the nervous system may be affected, and is probably the channel of its impression, yet that the deleterious effects of an elevated temperature, when respiration is stopped, depend on its stimulating the capillary circulation of the system, and thus promoting the de-oxygenation of the blood, that change which is antagonistic of respiration, which rules its extent under all circumstances, and which, in fact, constitutes the necessity for having a respiration. But, whatever view we take of this point, the fact of the influence of temperature on asphyxia proves that the application of heat ought to be avoided until respiration is thoroughly established, when it will, no doubt, be a useful auxiliary to restore sensibility and renovate the patient.
The number of children that die of asphyxia at the time of birth is very considerable. Writers on midwifery have stated that one-twentieth of the children brought forth are still born, and of these a large proportion are asphyxiated, from various causes, often at the very moment of birth. The first measures that are generally and very properly adopted, when a child is born in a state of suspended animation, are to admit the cool air to its skin, to dash a few drops of cold water on it, and use similar means to arouse sensibility, more especially that of the nerves of respiration. From the great vascularity and sensibility of the skin, and the thinness of the cuticle of newborn children, great benefit may be expected from the access of air to the surface of the body. Immersion in warm water is sometimes had recourse to, and I have seen it completely successful in two or three instances, after the means just enumerated had failed; but this is a dangerous measure, one which, if it do not succeed, will quickly extinguish any possibility of recovery which may exist, as we have already seen. The great object in this, as in every case of asphyxia, is to establish respiration; and if the patient cannot be roused to perform natural breathing, artificial respiration must be had recourse to as quickly as possible.
Several eminent authors on midwifery recommend breathing into the lungs of the child, if other means are not at hand; but not much good can be expected from a measure which would undoubtedly suffocate a living child, and where there is any disposition to natural breathing this will be decidedly injurious. Allen and Pepys found that air which had been once breathed contained about 8 per cent of carbonic acid, and that if the same air were breathed over and over again till suffocation was felt, it would contain but 10 per cent of the same gas.
The apparatus in ordinary use for artificial respiration is the bellows; but this, although much better than blowing with the breath, is liable to many objections: first, there is danger of injuring the texture of the lungs by over distension; then there is a difficulty of expelling the air from the lungs after it has been injected; and the delay occasioned by thus expelling the air, by pressing on the chest and abdomen, renders it impossible by means of bellows to imitate natural respiration, in which there is a constant current of air to and fro in the lungs.
Mr. Read [of Regent Circus] was introduced to this society three years ago, by Dr. James Johnson, when he laid before us an invention for performing artificial respiration much superior to the bellows. It consisted of a syringe for exhausting the lungs by the mouth, the nostrils in the meantime being held, when, on removing the pressure from the nostrils, the chest expanded again by the natural elasticity and resiliency of the ribs, muscles of respiration, and pulmonary tissue, causing a tendency towards a vacuum; and the air instantly entered by the nostrils, from atmospheric pressure, as in a natural inspiration; when it was again withdrawn by the syringe, and became renewed in the same manner. I at that time considered whether the same plan could not be adopted for the restoration of still-born children; but there were insurmountable difficulties. The lungs were in this case empty, to begin with; and even if one should commence by an artificial inflation, the chest could not be expected to take on all at once that resiliency which it acquires in after life, no doubt from the fact of the lungs never being again emptied after respiration first commences. So the matter rested, until a short time ago when Mr. Read, knowing I took an interest in the subject, called to shew me an improvement in his apparatus, which indeed he had brought to such perfection, that the use of it on himself would supersede his natural respiration for an hour together without inconvenience. I then suggested that he should make a little instrument on exactly the same plan, adapted to the size of new-born children. It consists of two syringes, one of which, by a tube adapted to the mouth, and closing it, withdraws air from the lungs, and the other syringe returns the same quantity of fresh air through a tube fitted to the nostrils. The two pistons are held in the same hand, and lifted up and pressed down together, the cylinders being fixed side by side, and each having two valves. When the pistons are raised, one cylinder becomes filled with air from the lungs, and the other with fresh air from the atmosphere, which can be warmed on its way by passing through a tube and metal coil placed in hot water. When the pistons are depressed, the latter cylinder is emptied into the lungs, and the air in the former is ejected into the atmosphere. In this way a constant current of air to and from the lungs is maintained, as in a natural respiration. The introduction of warm air is no doubt a great advantage. The objections to the application of heat during asphyxia cease, so soon as there is a proper supply of air to the lungs; and in introducing heat in this way, it must be remarked that we are only warming that blood to which we are at the same time imparting its arterial properties. This artificial respiration should be persevered in for some time, say an hour at least, [225/226] before we give up in despair; and if our efforts be successful, we should still persevere until the child is completely revived, and capable of carrying on a full and effective respiration of its own: for the secondary asphyxia which so often comes on, arises, in my opinion, from an efficient respiration not having been established, whence the blood remains in a badly oxygenated state, and does not rouse the nervous system to its full sensibility, but allows it to remain in a condition, so to speak, of not truly appreciating its own want of respiration. I know an instance where the breathing of a child was accidentally interfered with just after birth; and although not to the extent of producing asphyxia, respiration was never properly performed and the child died after a few hours.
Comparing the weight and size of the lungs of a new-born child to those qualities of adult lungs, the former may be expected to contain nine or ten cubic inches of air. Each cylinder of the instrument before the society contains an ounce and a half by measure, or somewhat less than three cubic inches; it can consequently be used without the lungs ever being either empty or distended. In the case of a still-born child, I should recommend that the exhausting syringe be used first to remove any mucus there may be about the fauces; then, since the lungs are empty, a little air may be injected with the other syringe, before beginning with the pistons raised to work the two syringes together.
An accoucheur can scarcely be expected to have an instrument with him at every labour; but it fortunately happens that the danger of asphyxia to the child is frequently foreseen, sometimes before the conclusion of labour; since it may be apprehended in all preternatural presentations, in cases of hæmorrhage, in difficult parturition, and from various other causes. The instrument may be useful likewise to perform artificial respiration in poisoning with opium, ardent spirit, or prussic acid, in sudden death from fits in children, and in other cases which will suggest themselves. The syringes can be separated and used as stomach or enema pumps, with the appropriate pipes that are supplied.
Oxygen gas is sometimes mixed with the air to be thrown into the lungs of asphyxiated persons. I imagine that with a good artificial respiration, such as this instrument will supply, atmospheric air will be sufficient without additional oxygen: if however, it be deemed advisable, oxygen gas can be generated in great purity, in a few minutes, from chlorate of potash, by means of a spirit-lamp and a small retort, and can be mixed in any quantity with atmospheric air in one of the bags belonging to the instrument. No harm can arise from thus using oxygen, unless it should be continued for some time after recovery.
With respect to electricity, the form of galvanism is the most convenient one in which to apply it; and there can be no harm in administering slight shocks after these other means have failed. But the chief intention of electricity is to excite the respiratory movements; and this is fulfilled by an efficient artificial respiration. I believe that oxygenating the blood in the lungs is the most effectual means to restore the action of the heart; and that it will restore it if that organ retain any irritability, and the blood be not coagulated. The elasticity of the pulmonary arteries will probably enable them to expel a little of the blood with which they are distended through the capillaries, so soon as the re-establishment of the chemical changes will allow it to pass; and this reaching the left side of the heart, may restore the functions of that organ. As an instance how long the heart may retain its muscular irritability, and the effect of respiration on it, I may mention an observation I made on a guinea-pig which I drowned. It died in two minutes; and when it had been dead an hour, I opened the chest and found the right side of the heart distended with blood, the left side not containing much, and the heart was perfectly still. In a little time the surface of the lungs became changed in colour, from the air imbibed through the pleura pulmonalis; and I was surprised to observe a slight vermicular motion in the right auricle. I divided the trachea, and performed artificial respiration, and shortly observed that the ventricles began to move, and that some bright red blood was visible through the coats of the left auricle. Rhythmical contractions of the heart continued for three-quarters of an hour, at the rate of twelve in [226/227] the minute. The contractions, however, were not complete, and the blood was not expelled from the heart. I found, on opening that viscus, that there was coagulated blood in all its cavities.
Physiologist have amused themselves in speculating on the cause of the first respiration; but doubtless it is the same as of the second and third, and all the succeeding respirations; namely, a sensation or impression arising from a want of oxygen in the system, and conveyed to the medulla oblongata, either by the blood circulating in it, by the nerves in connection with it, or by both causes. The placenta undoubtedly performs for the fetus the office not only of the lungs, but of all the great excretory organs; and so long as the placenta performs its functions, the fetus is perfectly at ease and feels no need of respiration; but whenever this communication between the child and its mother is interrupted, at least in the latter months of pregnancy, the child, as every accoucheur has experienced, makes convulsive efforts at inspiration, similar to those made by a drowning animal; efforts which would be successful inspirations provided the child were in an element which would be admitted by the glottis. Moreover, I have remarked that even a strong child does not always begin to breathe the minute when it is born; but if the umbilical cord be pressed between the fingers it will instantly draw an inspiration.
It is an interesting question how long a complete interruption of the placental functions may have place in a child at full term, before all signs of life will disappear, and a state of suspended animation be produced. Moralists have often asserted that human beings come into the world in a more puny and helpless condition than any other animals; but in this they are mistaken; for, without including marsupial animals, the young cats, and all those that are brought forth with their eyes closed, cannot maintain life without artificial heat, which they receive by lying close to the mother: in fact they can scarcely be said to have a proper temperature of their own. A child born at the full term, on the contrary, can maintain its temperature if well protected from cold. Now Dr. Edwards has proved that the necessity of respiration is intimately connected with the power of generating caloric: kittens and puppies will linger for half an hour or more in water at a favourable temperature; but those young that are able to maintain their own warmth do not possess much advantage over adults in their power of resisting asphyxia. But even new-born kittens, in water at the heat of human blood, do not live more than ten minutes; so that a fetus in the uterus, at a temperature of one hundred degrees, or rather more, must be very soon reduced to a state of complete asphyxia; and the experience of medical men, I believe, pretty well coincides with this conclusion. With a seven months' fetus it will be somewhat different, as it is more in the condition of those young that require artificial heat. The new-born child, however, from its open foramen ovale, and the great vascularity and sensibility of its skin, probably possesses some advantages over the adult in its capability of being restored from apparent death.
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7. On paracentesis of the thorax.
Source: Snow, John. London Med. Gazette, vol. 29, Jan. 28, 1842, pp.
705-707.
By John Snow, M.R.C.S. for the London Medical Gazette, read at the Westminster Medical Society on December 18, 1841.
In the normal condition there is no vacant space within the thorax. The pleura on each side of the chest is an empty bag, merely lubricated on its inner surface with serum; and the pulmonary and costal portions glide gently over each other during respiration. Whenever any fluid, whether a liquid or a gas, accumulates within the pleura, it is desirable that we should get rid of it. Tapping the thorax, however, is the means adopted only in those cases in which the fluid is known or presumed to be pus, or where there is serum or air in one pleural sac in such quantity that one lung is rendered useless, and the mediastinum is pushed aside, and the function of the opposite lung so interrupted, that life is endangered. Under other circumstances than these, the ordinary modes of performing paracentesis of the chest, whether by the trocar or the bistoury, would not diminish the existing evils.
The tissue of the lungs possesses an elasticity which would enable these organs to expel the greater part of the [705/706] air they contain, provided the atmospheric pressure were exactly equal on their internal and external surfaces; but so long as the thorax remains intact the atmosphere can only press on the exterior of the lungs through the walls and floor of the chest, and the muscles of respiration being more powerful than the elasticity of the lungs, the atmospheric pressure on the interior of the latter compels them to be obedient to every motion of the chest. But so soon as an artificial opening is made into the pleura, the atmospheric pressure is at once equal on the inner and outer surfaces of the lung on that side; it collapses in accordance with its own elasticity, and remains unaffected by the motions of the ribs and diaphragm; and whether the air press immediately on the surface of the lung, or through the medium of a liquid effusion, the effect will be the same. It follows from this, that at the conclusion of paracentesis, performed in the ordinary way, the lung must be collapsed, and the space between it and the ribs occupied by air, provided all the liquid has been removed. And, in fact, with the stethoscope applied to the chest during the operation, the air can be heard passing in by bubbles as the liquid flows out.
The introduction of air into the pleura will most likely be injurious whenever that membrane is in a state of inflammation; but the greatest evils arising from the admission of air, are occasioned by its mechanical resistance to the expansion of the lung, which can only be brought into perfect use in proportion as the air contained in its pleura is absorbed; and the complete absorption of it must occupy several days. During this time, not only does the patient suffer from limited respiration, but time is allowed for the lung to become bound down by the consolidation of the coagulable lymph, which may be effused, and thus permanently detained within its shrivelled dimensions. The removal of serum whilst in moderate quantity, and recently effused from pleurisy, would prevent the diminished lung and contracted chest which often follows that complaint, provided the serum could be removed without being replaced by air, otherwise the operation would obviously not be of much avail. When from pneumothorax or effusion of serum, the lung is pressed close to the spine, the mediastinum pushed to one side, and the ribs and intercostal spaces distended, the common operation of paracentesis gives great relief, because it allows the thorax to return to a state of equilibrium, and relieves the other lung; the patient being brought to the condition a healthy person would be in after having an opening made into the pleura and then closed again, the air being allowed to remain. But even in these cases, or where purulent matter is effused, it would be a great advantage to leave the patient with the pleura empty, and the lung expanded and filling the chest.
To make an opening into each pleura, and allow both lungs to collapse, would be to cause instant death by asphyxia; accordingly, the two sides of the chest cannot be tapped by the ordinary method on the same day. And when dyspnea exists from liquid in both pleuræ, the patient cannot dispense with one of his embarrassed lungs; he evidently could not live with half the respiration he has got; accordingly paracentesis is not performed in hydrothorax, a disease which nearly always occupies both sides of the chest. Idiopathic hydrothorax is believed to be very rare, if it exist at all. If there be such a complaint, it will probably, like hydrocele, be generally single, and occupy but one side. Hydrothorax, however, arising from some other affection, such as obstructed circulation through the lungs or heart, or disease of the kidneys, is a frequent complaint, and one which, if not relieved by medicine, soon proves fatal. It is sometimes but a symptom of the approaching dissolution which would take place independently of the dropsical effusion; but at other times it cuts off the patient much sooner than would the original affection of the heart or other organ. The dropsy arising from granular degeneration of the kidneys may occur in any stage of the disease; it generally involves nearly all parts of the body, but it may predominate in one situation, as in the cellular tissue, in the abdomen, or the thorax; and when in the latter situation may soon be fatal; and this may occur either in an advanced stage of the disease, or when there is merely a state of inflammation or congestion of the kidneys, which might lead to granular disease if not removed by [706/707] remedies. In a case of renal dropsy followed by scarlet fever, which occurred to me two years ago, the child was cut off by hydrothorax, although it was not worse in other respects than some who recovered.
Now, provided the serum can be removed without making a communication between the external air and the pleura, I do not see why tapping may not be performed on the thorax with the same safety and success as on the abdomen. I find from a recent number of the "London and Edinburgh Monthly Journal," that Dr. Davidson, of Glasgow, has been applying cupping-glasses over the canula introduced for empyema, in order to withdraw the fluid and prevent the ingress of air. This is certainly an improvement, but still leaves the operation far from a state of perfection; for, not to mention other objections, it is obvious that on the removal of the cupping-glass, air must rush into the chest before the canula can be withdrawn, or other means taken to stop the opening; and many cubic inches of air will rush through a very small orifice in half a second. Accordingly, in a case Dr. Davidson relates, the splashing of fluid was heard on performing the Hyppocratic test of succussion, three days after the operation, and we know this splashing can only take place when there is both air and liquid in the thorax.
The chief object of this paper is to lay before the Society the drawing of an instrument, which any member can get made by his own instrument maker.* By its means any fluid can be withdrawn from the chest, without making a direct communication between that cavity and the external air. It consists of trocar and canula with a stop-cock in it, the trocar to pass through the open valve of the stop-cock. A portion of the trocar must be made perfectly cylindrical, and to fit accurately the whole length of the canula. In withdrawing the trocar from the canula after their joint introduction, it must be brought so far as to be clear of the stop-cock, which point is indicated by a mark on the trocar, and then the stop-cock must be turned before the complete removal of the trocar. The portion of elastic tube must now be screwed to the canula; and to this tube must be screwed a double action syringe, with two distinct valves, like a stomach-pump. The valve of the stop-cock can now be reopened, and by working the pump, the contents of the pleura, whether gaseous or liquid, will be withdrawn. It is evident that not a particle of air can enter the pleura, and that the integrity of the chest as a pneumatic apparatus is not impaired during the operation. Before introducing the trocar, the skin must be drawn a little from its situation, and then by withdrawing the canula slowly at the end of the operation, the correspondence between the superficial and deeper wounds will be lost before air can enter the pleura.
If the lung be already firmly bound down before resorting to the operation, in a case of effusion, it will not be practicable to draw off the whole of the liquid. In such a case the resistance to using the pump, and the sense of uneasiness in the patient, will indicate when to stop, as in using the enema pump; and if the liquid be serum, it will be preferable to leave a little in the thorax; if, however, it be pus, the pump can be removed, and air admitted to allow of its complete removal.
This instrument must possess great advantages in the cases in which paracentesis is at present performed, and it will extend the occasions on which the operation may be resorted to with safety and advantage.
54 Frith Street, Soho Square.
*It has since been manufactured, under my directions, with great accuracy, by Mr. Read, of Regent Circus.
[A drawing of the instrument was forwarded to us with the paper, but the description is so distinct, that we have not thought it necessary to have an engraving made. - ED. Gaz.]
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8. Response to: "Uterine haemorrhage, with retention of the placenta"
Source: Snow, John. London Medical Gazette, 11 November 1842, 224-25 [Letter to Ed.].
To the Editor of the Medical Gazette.
Sir,
I some time ago saw an article in one of the medical journals on a method of expediting delivery. I have forgotten in which publication it was, and have spent a great deal of time in looking for it, in order that I might refer to it in this communication, but have not succeeded. It was, however, to the effect that the author, in cases of protracted labour from inefficient pains, had found benefit from introducing two fingers into the vagina, and pressing against its posterior part during a pain, in imitation of the bearing down of the child's head on the perineum; and he attributed the good effects--no doubt rightly--to what is called the excito-mototry function of the nerves.
I have not tried this plan previous to the birth of the child, but I have found it useful on what is, I think, a more important occasion--retention of the placenta from inaction, or insufficient action, of the uterus, especially when this is complicated with hæmorrhage. The following is an outline of one out of two or three cases:--
I attended Mrs. D. in labour about a month ago. She is the mother of a number of children, and her last four labours have been accompanied with flooding after the birth of the child. At her last previous confinement, two years ago, I was present, and the hæmorrhage between the delivery of the child and that of the placenta was such as to cause debility, and greatly to retard her recovery. On the present occasion she was in a very weak state from an affection of the hip-joint, and, owing to the feebleness and inconstancy of the pains, the child was not expelled till a fortnight after the os uteri first began to dilate. After the birth of the child, gentle traction of the funis, and firm pressure over the region of the uterus, were made for some minutes, without inducing any uterine contraction; and as there was considerable and increasing hæmorrhage, I introduced two fingers into the vagina, and made firm and continued pressure on the perineum with them. The uterus commenced to contract the instant this pressure was applied, and the contraction continued till the placenta, together with some coagula, were expelled, when the hæmorrhage at once ceased, and the uterus remained properly contracted.
This is a very easy measure, which can be put in force in a moment, and need not interfere with any other efforts either to promote contraction of the uterus or to check hæmorrhage. I feel satisfied, however, that it may often be of service, and that it may occasionally obviate the necessity of introducing the hand into the uterus. The liability of tenesmus to induce premature labour, and the increase of uterine action from plugging the vagina, are, no doubt, physiological phenomena indentical [sic] with the one under consideration. I do not, however, propose that the above expedient should supersede the plug on any occasion where the plug is admissible.--I remain, sir,
Your obedient servant,
John Snow
Frith Street, Soho Square,
Nov. 3, 1842.
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9. On the circulation in the capillary blood-vessels, and on some of its connections with pathology & therapeutics.
Source: Snow, John. London Med. Gazette, vol. 31, Mar. 3, 1843, pp. 810-816.
By John Snow, M.R.C.S., for the London Medical Gazette. (*This article has been selected and re-arranged from two papers read by the author at the Westminster Med. Soc. On Jan. 21st, and Feb. 4th.)
The heart not the only cause of the circulation.--The various functions assist the capillary circulation.--Circulation in plants--in the more simple animals--in asphyxia.--Contraction of vessels does not assist the circulation.--Diapnets, or medicines which promote respiration.--Cutaneous transpiration.--Inflammation
The blood, after leaving the left ventricle of the heart, passes through tubes which divide and subdivide until they become of microscopic smallness, before they re-unite to convey the blood to the right side of the heart; whence the whole of that fluid has again to pass through a similar arrangement of vessels in the lungs, before it reaches the point from which we set out. It is in the minute branches that all the changes in the blood, and the reciprocal changes between that fluid and the rest of the organism, take place; the heart and larger vessels merely serving the mechanical purpose of transmitting the blood. These ultimate or smallest branches, which have obtained the name of capillaries, seem in most of the tissues of the body, quite distinct in arrangement and appearance from the arteries which bring the blood from the heart, and veins which return it to that organ. Viewed by the microscope, they are seen to be of equal diameter throughout, intercommunicating with each other so as to form a net-work, and forming a union between the arteries and veins, but having no other openings or communications with any other parts.
There is considerable diversity of opinion with respect to the forces which circulate the blood. Many physiologists of great eminence maintain that the contraction of the ventricles is the sufficient and sole power which forces the blood through the capillaries and back again to the heart; whilst others are of opinion that various causes assist the heart to propel the blood through the vessels. I feel convinced that, besides the action of the heart, there is one other power of importance engaged in the circulation of the blood, a power which has been suggested and described with more or less of distinctness by Dr. Allison, Baumgartner, Koch, Dr. John Reid, and, I believe, other authors, but has not yet received that general assent, or even consideration, which it deserves. The opinion to which I allude I will define as follows:--that the mutual changes which take place at the capillaries, between the blood and the tissues, are attended with attractions and repulsions which assist to impel the blood in a definite direction. Some of the fluid part of the blood is continually passing through the invisible pores of the capillary vessels to nourish the surrounding solids, whilst, at the same time, a fluid, containing in solution the tissues decomposed in supporting the vital functions, enters the capillaries from without: in various parts exhalation and imbibition of liquids and gases are going on, and in others special secretions are separated from the blood. The opinion, then, which I advocate is, that all these actions assist the circulation of the blood; in short, that every function promotes the capillary circulation of the part in which it takes place.
Towards establishing these views, I shall first shew that the causes to which I have alluded are alone sufficient to move a nutritious fluid in capillary tubes.
The isolated cells of chara, and of most simple vesicular plants, are filled with a liquid which contains globules visible by the microscope. These globules move round in their respective [810/811] cells, each cell having a separate circulation of its contained fluid. There is no contraction of the walls of the cells and indeed, there is no conceivable cause for this circulation, except the process of nutrition going on in the cells. In the higher plants, in which the sap moves in capillary tubes and spaces, there is no contraction of the vessels, nor any other mechanical force to cause the circulation. Absorption by the spongioles of the root can raise the ascending sap to a limited extent only; when the root is cut off, and the stem put in water, part of the water is raised into the plant; and indeed, the ascent of the sap may be observed in spring to commence first at the buds, the fluid lower down afterwards following: it follows, then, that the functions, going on in the leaves are the chief cause of the ascent of the sap. In the leaves the course of the fluid is changed, and the elaborated sap returns towards the root, nourishing the plant, and forming various secretions in its course; and this course is not always a descending one, for in a great portion of many plants the returning sap has to travel in opposition to the force of gravitation. It is evident, therefore, that the circulation through the leaves, and back again towards the root, is accomplished by the exhalation and imbibition of the leaves, the change of composition and other functions performed there, and by the nutrition and secretion taking place as the sap returns--by some or all of these functions--since there are no other causes, except, indeed, capillary attraction, which cannot cause the circulation, but only aid it to a small extent.
In many species of the lowest tribes of animals, the circulation of the blood which takes place in capillary tubes is independent of contractions and all mechanical forces, and must arise from the functions taking place in the vessels: for instance, the trematoda, an order of intestinal worms, possess two vessels on each side of the body, in which the blood moves in opposite directions; and, according to the observations of Ehrenberg and Von Nordman, these vessels do not contract in the least. The greater number of animals in the lowest classes have, it is true, some vessels which contract; but these contractions are often very feeble compared to the extent and vigour of the circulation. The motion of the ambient liquid over the surface and through the canals of sponges, likewise tends greatly to strengthen the views under consideration; for since no contractions or ciliary motions can be detected in these beings, the currents must be caused by the nutrition, respiration, and other functions taking place on the surfaces of the sponge. And it may be mentioned here that when development first commences in the higher animals the circulation is independent of any mechanical impulse: it has been clearly shown by Von Baer that the blood is formed before the vessels, and that its first motion is towards the heart, and not from it.
The next point in this inquiry which I shall take up, will be, to ascertain whether the action of the heart is of itself sufficient to effect the circulation; and it is only necessary to pay attention to the phenomena of asphyxia to perceive that it is not. When those changes in the blood which take place at the lungs are prevented by stopping the access of oxygen, the passage of the blood through the lungs is at once greatly diminished, and is shortly arrested, whilst the heart continues to act some time longer. It matters not whether the lungs are collapsed or distended, or whether the respiratory motions are continued or not; if the characteristic change in the blood is prevented, the right ventricle of the heart is unable to propel the blood properly through the lungs. There is no mechanical impediment, the blood is not coagulated, as the fact of recovery, if the cause of asphyxia be timely removed, proves; the only conclusion, then, is, that the change in the blood from venous to arterial being necessary to its free passage through the lungs this change must generate forces which assist its passage. In his experiments on asphyxia in dogs, Dr. John Reid found (Edin. Med. and Surg. Journ. No. 147.), by the aid of M. Poiseulle's instrument, the hæmadynameter, that during the first moments of asphyxia the pressure on the systemic arteries was increased, and consequently that there was obstruction in the capillaries of the general circulation: from which it appears that the small quantity of blood which does pass through the lungs, being but little altered from its [ 811/812] venous state , is not fitted to undergo those opposite changes which take place in the body at large; and the left ventricle is but ill able to propel it through the capillaries for want of the auxiliary forces arising from those changes.
On the other hand, a circulation sufficient to support growth and formation of parts to a considerable extent, may be maintained without the assistance of the heart. The proof of this consists in the existence of human acephalous monsters without heart, many of which have been developed in a uterus which contained no other fetus at the same time, the contraction of whose heart might be supposed, by a union of the placental vessels, to aid the circulation; and in these cases there was consequently a double capillary circulation, the placental and general one, both independent of a heart. In one remarkable case related by Emmert, the uterus merely contained a limb attached to the placenta by a funis.
That other agencies are at work, assisting or controlling the circulation, is evident from a single fact, admitted, I believe, by all recent observers with the microscope, viz. that the colourless corpuscles of the blood do not move through the capillary vessels with the same speed as the red globules, but roll slowly along near the sides. And to complete the proof of the opinion with which we set out, it is only necessary to shew that there are no other causes which can assist the heart to move the blood besides those we have stated.
Many authors, perceiving the immense force that would be required to impel a fluid through such small tubes as the capillary blood-vessels; considering the portal circulation, where the blood is collected from these minute vessels and again passes through a similar set before it returns to the heart; considering the circulation in fishes, in which the blood all passes through the capillaries of the gills, and afterwards through those of the system, before it again reaches the heart; and considering, likewise, the circulation of monsters without hearts, and perceiving difficulties in all these and other considerations, have admitted the inability of the heart to circulate the blood, but have suggested contractions of the capillary vessels, or of the arteries, as the forces which assist the circulation. Now contraction of the capillaries would impede the entrance of blood into these vessels as much as it would facilitate its exit on the other side; and consequently could be no assistance to the circulation--unless, indeed, it were, as Mr. Julius Jeffreys suggests (Med. Gaz. March 18, 1842), a vermicular contraction; and that no such contraction as this exists is evident on observing the capillary circulation with the microscope. The same is true of the arteries; the pulse proves that there is no vermicular or progressive contraction in them, and any other contraction would resist the action of the heart quite as much as it could assist the flow of blood towards the veins. The elasticity of the arteries modifies the impulse of the heart exerted on the blood, and causes its current to be continuous; whereas if it had to pass through rigid tubes it would stop between each stroke of the heart. But this elasticity can apply no additional power to the circulation; it only acts the part of a regulator of the motion. The arteries, in addition to their elasticity, which continues after death, possess a tonic or vital contractility, which enables them to accommodate themselves to the altered quantity of blood and to different states of the circulation. This contractility I believe to be under the influence of that system of nerves which accompanies the arteries everywhere and is distributed to their coats,--I mean the ganglionic system, or great sympathetic,--and I consider that it has great influence over the quantity of blood which reaches different parts, and over the state of the circulation, both in health and disease; but it cannot assist the circulation by adding any power to it; it can only modify the application of other forces. The capillaries themselves can alter their size, and thus modify the circulation which they cannot assist; they do so on the application to them of various medicinal and physical agents.
Direct observations made with the microscope favour the doctrine I advocate, since Spallanzani and many later physiologists have seen the blood move in the capillaries of the frog for a length of time after the removal of the heart; and I conceive the conclusion to be drawn from these observations cannot be weakened by the negative [812/813] evidence of others, who have observed the blood not to move under similar circumstances.
There is an experiment by Magendie to which it will be well to allude, since it is considered by that eminent physiologist, and many others, to amount to a proof that the heart's action is the sole cause of the motion of the blood in the veins; but a careful examination of that experiment will shew that it is not unfavourable to the views here entertained, and that, at the utmost, it only proves, what no one would attempt to deny, namely, that, when the blood is prevented from reaching the capillaries, it cannot flow through them. The following is an account of the experiment in the author's own words. "After having passed a ligature round the thigh of a dog, as I now described, that is, without including the crural artery or vein, apply a ligature separately upon the vein near the groin, and then make a slight opening in this vessel. The blood will immediately escape, forming a considerable jet. Then press the artery between the fingers to prevent the arterial blood from reaching the member. The jet of venous blood will not stop on this account; it will continue some instants; but it will become less and less, and the flowing will at last stop, though the whole length of the vein is full. If the artery be examined during the production of these phenomena, it will be seen to contract by degrees, and will become completely empty. The blood of the vein then stops; and at this period of the experiment, if you cease to press the artery, the blood injected by the heart will enter, and as soon as it has arrived at the last divisions, it will begin to flow again at the opening of the vein, and by little and little the jet will be established as before." The movements of the chest in respiration give a little assistance to the return of blood to the heart; but it is only on the large veins in the immediate vicinity of the chest that these movements can have any influence; in natural respiration this influence is very small, and under no circumstances can it extend to the capillaries; therefore it need not occupy much attention in this paper. I have now, I think, considered this subject in all its bearings, and have, I trust, proved that the heart, although, undoubtedly, the chief cause of the circulation, is yet materially assisted by other forces situated at the capillaries; not by any contractions of these vessels, or by any other mechanical power, but by forces arising out of the functions in the capillaries and in their immediate vicinity. I have nothing to advance respecting the intimate nature of the attractions and repulsions which accompany the changes of composition at the capillaries, and which tend to move the blood in a definite direction. I have carefully avoided such terms as chemical, electrical, and vital, both in order that I might not be misunderstood, and because I look upon chemical affinity, electricity and vitality, rather as expressions which are useful to us in the infancy of science than as forces which have a separate and defined existence. Our ignorance, however, of the ultimate cause of these attractions is no argument against their existence; since we admit many laws in science of the causes of which we are ignorant.
The views of the circulation entertained in this article will enable us to explain many phenomena in physiology and medicine which would otherwise be a mystery; of which I will give two or three examples. Assafetida, ether, various essential oils, camphor, and other volatile medicines, relieve difficult and impeded respiration; they are sometimes called antispasmodics, but they give relief in various cases of obstructed pulmonary circulation when no spasm is even supposed to exist, and I do not know by what modus operandi they can be beneficial except by one in accordance with the above views of the capillary circulation. They are all separated from the blood in the lungs and escape with the breath; they leave the lining membrane of the air-cells in the gaseous form with the carbonic acid gas and watery vapour, increasing very much the quantity of vapour which exhales from the pulmonary capillaries, and thus give additional impetus to the blood; in this way lessening congestion and relieving its attendant distressing symptoms. As this class of medicines promote the function of respiration I will venture to call them diapnetics, from ??? and ????. To call them expectorants would not be correct, as expectoration is not respiration. As the greater number of diuretics are voided with the urinary excretion, the above class of medicines resembles them [813/814] in this respect, since they pass out of the body with the excreted carbonic acid gas and aqueous vapour. A dry atmosphere gives relief in some forms of asthma; it promotes the excretion of watery vapour, and acts in the same way as the above medicines.
MM. Breschet and Becquerel have recently found that on applying impermeable substances to the skins of animals, and thereby preventing the cutaneous transpiration, the animals gradually decreased in temperature, and appeared to die of a kind of cutaneous asphyxia. I do not know that these gentlemen have offered any explanation of this circumstance, and I do not see that it is capable of any, except that afforded by the views which it is the object of this paper to support. Exudation of water and watery vapour being one important function of the skin, it follows that, this being stopped, the cutaneous circulation is slackened, and along with it the other functions of the skin, the most important of which is the evolution of caloric. We need not expect sanguineous congestion of the skin under these circumstances, since there are plenty of other channels for the blood; the skin being in this respect very differently situated from the lungs. The evaporation of the cutaneous transpiration is attended with the abstraction of caloric, and this evaporation can preserve the body under extraordinary circumstances from being raised above the temperature compatible with life; as I believe, was first shewn by Franklin: but we learn from the experiments of Breschet and Becquerel that, under ordinary circumstances, the cutaneous transpiration is the cause of a generation of caloric much more than sufficient to over-balance the abstraction of heat arising from its own evaporation. Dr. Willis has been good enough to direct my attention to a note to his translation of Wagner's Physiology in which he states his opinion that one use of the cutaneous secretion is to assist the capillary circulation. That such is the case, and that the fall of temperature in animals experimented on by Breschet, was the direct effect of the arrest of transpiration from the skin, and not a consequence of some injury to the system at large, I satisfied myself by folding one of my arms in oil-skin under the usual clothing; for I experienced a sensation of coldness all the afternoon it was applied, and on its removal the arm was found to be evidently colder than the other. It is generally taught that in fever with a hot and dry skin there is diminished cutaneous transpiration, but, reasoning by analogy from the above facts, we may conclude that such is not the case, and that the secretion from the skin is at least equal to, if not greater than, what it is in health; and, that such is really the case, a little consideration will prove; for the patient drinks a good deal, voids but little urine, does not increase in bulk, but on the contrary, gets thinner; therefore, there must be increased evaporation from the skin and lungs, for which the elevated temperature of the body is sufficient cause. The heat of the surface, which is sometimes considered as a consequence of diminished evaporation, accounts satisfactorily for the dryness of the skin, where the cutaneous secretion is not very great indeed, by the increased rapidity of evaporation it must produce. The moisture of surface produced by antimony and some other diaphoretics, I conceive, arises from the property these medicines have of reducing the temperature of the body, and not from increased determination to the skin. I admit that this position respecting the perspiration in fever requires to proved by experiment; but in the meantime, I feel so satisfied that the evaporation from the lungs, which is confined by physical laws, cannot be sufficient to dispose of all the supplementary fluid, that I have no doubt, in my own mind, on the point.
The above views of the circulation afford, I think, a better explanation of the phenomena of inflammation than do any other. Increased function, which, according to these views, necessarily accelerates the circulation of a part, may lead to inflammation; as, where excitement of the passions of the mind causes phrenitis, or, where the intensity, or long-continued application of light causes, inflammation of the eyes: now, according to Dr. Kaltenbrunner and other eminent microscopical observers, the velocity of the capillary circulation is greatly increased in the early stage of inflammation. All observers, I believe, agree that the capillary vessels of an inflamed part are increased in size, or dilated: and [814/815] some authors, who consider the heart's action the only cause of the circulation, say that the current of blood through an inflamed part must be retarded in proportion to the dilation of the capillaries, since when a liquid is forced through a tube having one portion dilated, its motion is slower in the dilated portion. Were the contractions of the heart the sole cause of the circulation, this would be so, but then the temperature of inflammation would be the normal temperature; and if this disease consisted in a stoppage of the capillary circulation, as other authors say, then an inflamed part would be colder than the others: for whether we consider that the blood merely warms the body by distributing heat which it acquires from some internal source, or whether we adopt the view, which has been proved by various facts, that animal heat is chiefly evolved in the systemic capillaries, where the arterial is changed into venous blood; still, to account for the elevated temperature of inflamed parts, the passage of an increased quantity of blood through the vessels is necessary, since the external air and contiguous bodies are constantly conducting away the heat. One function, to which the capillary circulation is subservient, is the maintenance of sensibility; and when the circulation is accelerated to the amount of active inflammation, the sensibility of the inflamed part is increased into pain. The pain in this disease, I think, is generally in proportion to the natural sensibility; those parts which are most sensible in health being most painful in inflammation. It is probable that there are no living parts that have not an obtuse sensibility, although they may usually not have the opportunity of evincing it: thus, an alimentary bolus is generally not felt after it is swallowed; but if it be unusually hot or cold, or harder or larger than common, it may be felt all the way down the esophagus till it reaches the stomach.
The small arteries of an inflamed part become dilated as well as the capillaries, and often, also, the arteries leading to the part. This dilation of the arteries cannot be explained on mechanical principles, and must consequently depend on the nerves; most likely on the branches of the great sympathetic. Those who say that inflammation consists in obstruction of the capillary circulation, argue that this obstruction is the mechanical cause of the dilation and increased pulsation of the arteries; but obstruction could have no such effect unless it existed in all the capillaries of the system at once, as in asphyxia; for the pressure of the heart's action is exerted on all the arteries alike, and if the circulation were obstructed in one part, the blood would find an easy passage through others. Moreover, the compression of an artery causes no such dilation and pulsation above the compressed part as those of inflammation. The dilatation of the small arteries accounts sufficiently for the throbbing of many inflamed parts. In the state of health, the wave caused by the heart's impulse is stopped some distance before it reaches the capillaries; but in inflammation, the small arteries become so much enlarged, that the undulation caused by the heart's action reaches completely to the capillary vessels; and from the number of these arteries a pulsation is produced equal to that of a large artery in the normal state.
That inflammation is something more than an altered condition of the capillaries, or a loss of balance between these vessels and the heart, is proved by the fact, that the cornea, various articular cartilages, and other structures which contain no vessels of any kind are subject to this disease. Inflammation is a diseased process going on between the solids of the inflamed tissue and the blood circulating through it, or near it; and we find that this process has a tendency to change the structure and composition of both the solids and the blood; for there is good reason to conclude, from some observations made by Mr. Addison and others, that the increased formation of fibrine, in this disease, takes place chiefly in the inflamed part.
When inflammation proceeds so far as to produce disorganization of any kind, the circulation generally, I believe, becomes interrupted. But it is not my intention to enter at length into the subject of this disorder: I shall only make a few remarks on one or two points in the treatment before I conclude. According to the above theory of the circulation, it is very clear how perfect rest from the func-[815/816]tions of an inflamed organ, when it can be obtained, should greatly promote the resolution of the inflammation. The beneficial effects of local blood-letting are likewise apparent; for if the functions of an organ assist the circulation through it, when these functions are lowered by the abstraction of blood from the part, the capillary circulation cannot regain its wonted velocity unless some cause exist, or come into operation, to re-excite the morbidly increased functions of the part. On the other hand, if the circulation depended entirely on the vis a tergo, it is not evident how blood-letting from the vessels of the diseased part or those in its immediate vicinity, could do more good than the removal of the same quantity of blood from any other part of the body.
From what I have said respecting the effect of the cutaneous secretion on the capillary circulation, it follows that inflammation of the skin ought to be relieved by stopping the transpiration from the inflamed part; and this is an indication which may be fulfilled with safety and advantage in every case of inflammation on or near the surface. I believe it is on this principle that the benefit of water-dressings and poultices chiefly depends, as well as of lunar caustic and of flour to erysipelas; the former making a dead, and in a great measure impermeable membrane of the cuticle, and the latter likewise interfering with transpiration. The effects of stopping the exudation from the skin seem to reach some depth below the surface; for covering the mammary glands with large adhesive plaster is the most successful means I know of putting a stop to the secretion of milk, and thereby preventing the ill effects which might arise from its congestion in these glands.
Whilst, as was stated before, a dry atmosphere ought to give relief in asthma with passive congestion of the lungs, in inflammation of these organs the most suitable atmosphere should be one so charged with moisture that it can take up no more; and such an atmosphere is recommended by Mr. Jeffreys (Med. Gaz. Feb. 18, 1842), though on different principles, and has been found by him to be beneficial.
These are but a few of the subjects in medical science which are capable of receiving illustration and explanation from the above views of the capillary circulation; for one truth must always harmonize with all others.
Frith Street, Soho Square
Feb. 13th, 1843
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10. "A new kind of pessary"
Source: Snow, John. London Medical Gazette 7 April 1843, p. 100 [Letter to Ed.].
To the Editor of the Medical Gazette.
Sir,
I shall be obliged if you will allow me, through your pages, to call the attention of the profession to a pessary I have invented, which I believe to be preferable, in most respects, to all the various kinds at present in use. It consists of a piece of sponge cut into the form of a sphere, or, what is better, of an oblate spheroid, and tied up, by means of small twine or silk thread, in a circular piece of oil-skin, in such a manner that a small stem or tail is left half or three-quarters of an inch in length. The firmer kinds of sponge, which possess a good resiliency, are best; and the oiled silk is closed as firmly as it can be by tying, but no extraordinary means are used, by cement or otherwise, to make it completely impervious to air.
When this pessary is compressed in the hand, the air contained in the cells of the sponge is gradually forced out at the neck, between the folds of the oil-skin. In this form it can be very easily introduced; and when passed above the narrow part of the vagina and left at liberty, the elasticity of the sponge, and the pressure of the atmosphere together, cause air to re-enter the instrument, and it assumes its expanded form. The small tail hanging downwards will facilitate its removal at any time.
The chief advantages of this pessary are, I consider--
1. Its capability of being diminished in size during its introduction and removal.
2. Its softness, which is such that it can scarcely cause any of the effects of a foreign body.
3. Its small weight.
4. The tendency of its elasticity to keep it in its position; for any sudden pressure of the viscera above will be spent in overcoming this elasticity, instead of forcing the instrument through the external parts; and, moreover, such pressure will flatten it and make it wider, and thus render its extrusion the less possible.
As additional advantages I may mention its cheapness and its durability, which will be as great as that of the oil-skin; and this, if requisite, can be applied double.
I have applied this pessary with perfect success up to this time, in three cases in which the uterus, except in the recumbent posture, had protruded entirely beyond the external parts for a number of years; and in two of these cases various other pessaries had been tried, but in one case would not remain, and in the other could not be borne. As it is only about two months since I first applied these instruments, I will postpone any more particular accounts of the cases till another time.
Sponges are occasionally used as pessaries; but as they become charged with mucus and other fluids, and soon decay or become offensive, and a source of irritation, they are only resorted to as a temporary expedient. A small sponge dipped, from time to time, in some astringent fluid, and applied in the beginning of prolapsus uteri, when it is yet but slight, as Dr. Denman suggested with the object of performing a cure, may, I believe, often fulfil that desirable intention. The pessaries which I have hitherto used I have made myself; but I have now got Mr. Read, of Regent Circus, to make some, and he can supply them to medical gentlemen. Of course care will be required in adapting the size of those as well as other pessaries: when expanded these should be somewhat larger than a rigid pessary for the same patient.
I remain sir,
Your obedient servant,
John Snow, M.R.C.S.
Frith Street, Soho Square,
April 7, 1843
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11. Case of acute poisoning by carbonate of lead.
Source: Snow, John. London Med. Gazette 35, 22 November 1844, pp. 248-250.
By John Snow, Fellow of the Royal Medical and Chirurgical Society, (for the London Medical Gazette)
I was called between 9 and 10 o'clock on Wednesday morning, the 8th of May last, to Henry Woodley, aged 5 years, living at 1, Rose Stree Soho, and found him suffering with symptoms of poisoning. I ascertained that, on the Saturday night previous, he had eaten some white-lead ground up with oil, which another boy had stolen, under the impression it was putty, from the door of an oil shop in the neighbourhood, where it was exposed for sale. The quantity he had was not larger than a marble, and he did not eat it all, as a small portion was found on the floor afterwards. He complained of bellyache the next morning, and his mother gave him a dose of salts and senna: this did not operate, and the pain in the abdomen still remaining on the following day, she gave him rhubarb and jalap, and afterwards castor oil, and the bowels were opened on Tuesday evening for the first time. The child's mother did not think his illness serious, and did not mention it to me, although I was attending her husband; she thought what he had eaten was only putty, which was not poisonous. During Tuesday night the pain in the belly was increased, and vomiting commenced for the first time. On Wednesday morning I saw the child as I have stated. He was in great pain, which he referred chiefly to the scrobiculus cordis; he vomited constantly a brownish liquid containing streaks of blood; his skin was hot, and his pulse was 140 and hard; the face was swollen and of a purple colour; the conjunctiva were red, not only from injection of the vessels, but from blood extravasated and coagulated beneath the membrane; the nostrils contained blood, and the body was spotted with petechiæ; the gums were tense, shriveled, and milk white. Some leeches were applied to the epigastrium, and an emulsion containing Epsom salts was given. He passed some greenish-black semi-fluid motions of a very offensive odour. At 11o'clock the pain continued, with occasional vomiting; the pulse was small and the extremities were getting cold; there was palpitation of the heart. At 1 o'clock, on injecting the bowels I found that there was complete relaxation of the sphincter ani. The pulse at the wrist ceased shortly afterwards, the tracheal rale set in, and he died at 2 o'clock, about ninety hours after taking the poison. The heart beat above 100 strokes after the respiration. There was no delirium or other lesion of intelligence.
An examination of the body was made eighteen hours after death, in which I was assisted by my friend Mr. Marshall, of Greek Street, who took notes of the appearances. The cuticle was loosened from a great portion of the body, and a quantity of serum flowed from the nostrils on moving the head. The gums presented the white appearance observed before death; the pericardium was filled with serum deeply tinged with blood, and each pleura contained several ounces of similar fluid. The heart was soft and flabby, and there was a little red fluid blood in the ventricles. There was ecchymosis of the surface of the lungs, and they were engorged posteriorly. There were two spots of ecchymosis beneath the mucous membrane of the esophagus near its lower end; otherwise this tube was healthy. The stomach contained a little liquid similar to what had been vomited, and, throughout its entire extent, the mucous membrane was dark brown, swollen, and puffy, and there appeared to be extravasation of blood beneath it in addition to great injection of the vessels: this state did not extend to the duodenum or esophagus. There was a bright red injection of part of the cecum, but the rest of the alimentary canal was of the natural pale colour, and was not contracted in any part. It contained a little clay-coloured fecal matter in the form of small pellets. The kidnies were large and flabby, and the liver, which was of a darkish colour, instead of presenting its usual firmness, was like soft leather; it could not, however, be torn with greater ease than natural. There was a peculiar odour about the body; not that of putrefaction. The head was not examined. The matters vomited, and those found in the stomach and intestines after death, and likewise the substance of the stomach, were al[l] subjected to a careful chemical examination, but no lead, or, indeed, any other poison, was detected.
Although slow poisoning by white lead is very common, occurring to painters, and several other classes of workmen who use it or manufacture it, acute or sudden poisoning by this, or indeed any other salt of lead, is not common. They are seldom chosen for murder or suicide, and, although extensively used in various trades, they do not often lie exposed, like arsenic or oxalic acid, in such a shape as to be mistaken for any article of food or medicine. In the few authors to whom I have referred, I have not met with any fatal instance of poisoning by a single dose of carbonate of lead. Mr. Taylor mentions, in his Jurisprudence, the case of a woman, attended by Mr. Cross, who took six or eight drams of it, by mistake, for magnesia, and recovered by the use of remedies. Orfila gave half an ounce of it to a dog, and it vomited several times within twelve minutes, and was no worse afterwards; and Dr. Christison quotes from a German journal the case of a young woman who swallowed accidentally an ounce and a half of it, without any bad effects, either at the time or afterwards. That it is very poisonous, however, we have sufficient evidence; for the carbonate is the form in which lead is introduced into the system of painters, and of most artisans who suffer from it, and, generally, of those who are poisoned by water impregnated with this metal. The morning after this child had taken the poison, his mother gave him, as it happened, some Epsom salts amongst senna tea. Now sulphate of magnesia is an antidote for the soluble salts of lead, but as it does not act on the carbonate at ordinary temperatures, it could only be of benefit by neutralizing any portion which might be decomposed by the acids of the stomach, and unabsorbed at the time. Several hours had already elapsed when it was administered, and as it was not repeated, we need not wonder that it did not stop the fatal effects of the poison. In addition to emetics and the stomach pump, Mr. Taylor very judiciously recommends the combination of some weak vegetable acid, as vinegar or lemon-juice, with solution of sulphate of soda or magnesia, in cases of acute poisoning by carbonate of lead.
From what I could learn, this child appeared for three days to suffer only from symptoms of lead colic, viz. pain and constipation of the bowels; and the intense and general gastritis of which he died would seem only to have commenced, or at least to have become severe, about twelve hours before death, as it was not till then that vomiting came on.
When I saw the child, which was not till within five hours of his death, he seemed to be labouring under all the effects of a corrosive or irritant poison, which one would have supposed had been taken only a few hours, instead of nearly four days. In the case I have quoted from Mr. Taylor, and in those I have seen recorded, of poisoning by the other salts of lead in large doses, vomiting, and other symptoms of violent gastric irritation, came on soon after the ingestion of the poison. The comparative mildness of the symptoms in this case for three days probably depended on the incorporation of the white lead into a tough mass with oil, which might retard its operation, and cause it to act only by degrees, in proportion as it became digested.
The white, tense, and contracted state of the gums, is worthy of notice. The gums were white and excoriated in a case of poisoning by the acetate of lead, quoted by Mr. Taylor, when the patient recovered. Acetate of lead is administered, occasionally, as a remedy in mercurial ptyalism. Dr. Burton has directed attention to a blue line on the gums in persons suffering under the chronic influence of lead; and I have, in two instances, seen the gums severely ulcerated in painters who had not been taking mercury.
No lead could be detected in the body after death, or in the matters vomited: but we need not be surprised at this, when we consider that the patient survived till the fifth day. It is a negative result that has been obtained in other cases of death from this poison. He had been vomiting several hours before any thing was saved for examination, and the feces passed during life, which exhibited a peculiar colour, such as a mixture of sulphuret of lead with them might be supposed to occasion, were not subjected to analysis.
Frith Street Soho, Oct. 1844.
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12. "Case of malignant or haemorrhagic small-pox."
Source: Snow, John. London Med. Gazette 35, 31 January 1845, pp. 585-586, [Letter to Ed.].
By John Snow, M.D. London., Fellow of the Royal Medical and Chir. Society, (for the London Medical Gazette).
The following case from my note-book, of a form of small-pox which, I believe is happily now very rare, is, I think, not devoid of interest; and will be still less so, if examined in conjunction with the "Case of Pupura Hæmorrhagica, probably arising from variolous contagion, by N. Adams, Esq." in the last number of the Medical Gazette, which occurred in the country nearly at the same time as my case, and which resembles it in several particulars.
I was called at 7 o'clock, on the morning of Saturday the 8th of June last, to a boy named Cannell, living at No. 2, Chapel Place, Crown Street. He was a fine stout boy, seven years of age, but had been affected with asthma from his birth. His brother, aged 5, was labouring under small-pox in the same room; they were of the distinct kind, and in the maturative stage. Neither of the children had been vaccinated. The subject of this case took ill on the Thursday morning previous to my seeing him, with pain in the back, and fever. On the evening before my visit, an eruption appeared on the skin, and he became delirious; afterwards he had bleeding from the nose. He [586/587] was delirious all the night, and was insensible of what was said to him, and vomited a liquid mixed with blood. I found him in a muttering delirium, incapable of being roused, although he resisted any attempt to give him drink. He was vomiting almost constantly small quantities of blood, and of a thinner liquid, apparently serum, tinged with blood. The face and neck were swollen, and of a purple colour--were occupied, in fact, with one large vibex. There were other vibices on the body, and the rest of the trunk and extremities was spotted with numerous petechiæ, many of which had a lightish coloured spot in the centre, and appeared like pimples till they were touched, but there were only a very few on the trunk which could be felt to be a little elevated. The skin was hot, and the pulse frequent, small, and feeble; the tongue was coated with a brown fur, and the rest of the interior of the mouth was of a bluish white colour; he had passed motions in bed; cold applications were directed to the scalp denuded of hair, and sinapisms to the legs.
He was visited again in three hours; the vomiting of blood continued; the breathing was stertorous, and the pulse almost imperceptible. He died in half an hour more.
I made an examination of the body eleven hours after death, with the assistance of my friend Mr. Marshall, of Greek Street. The vibices and petechiæ remained as before; the scalp was very vascular, and blood flowed from it when cut; the veins on the surface of the brain were much distended, and the pia mater dipping in between the convolutions was much engorged, and there were little spots of extravasated blood in this situation. The red dots were found to be rather more numerous and large than natural on slicing the brain; there were one or two drachms of clear serum in each lateral ventricle, a little in each of the other ventricles, and a drachm or two at the base of the brain; the lungs were extensively emphysematous, they did not collapse on the chest being opened, but, on the contrary, rather bulged out, and many of the lobules were paler and more prominent than the rest. This emphysema of the air cells was most extensive at the lower part of the lungs; there were a few partial adhesions of the pleuræ, and the lungs were engorged with blood, as were the right cavities of the heart, which was healthy. The stomach contained a little bloody liquid, and all over its inner surface were dark purple spots averaging about the size of a pea, and situated about half an inch apart. They proved to be small portions of blood extravasated beneath the mucous membrane; this condition did not extend to the intestines. The feces in the small intestine were of a very dark colour, most likely from the presence of blood. The bladder was empty, and the viscera not mentioned were in the normal condition.
The row of small dwellings, in one of which this boy lived, are damp and ill ventilated, and all the illness I have seen in them has been more severe and intractable than in the rest of the neighborhood. I have treated two cases of sporadic cholera there, as bad as any cases of the epidemic disease which I have known to end in recovery; and one case of purpura hæmorrhagica with inflammatory symptoms in a child about five years of age, which I understand did not recover from the illness.
Frith Street, Soho Square, Jan. 22, 1845.
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13. "Pericarditis after scarlet-fever",
Source: Snow, John. London Medical Gazette 35, 7 March 1845, pp. 728-29 [Letter to Ed.].
To the Editor of the Medical Gazette.
Sir,
Dr. Somerville Scott Alison, in his article on the above subject, has alluded to several authors who have not, and to some who have, treated of the disease. I wish you to allow me the favour of stating, that I drew particular [728/729] attention to this subject in a paper on Dropsy after Scarlet-Fever, which I read to the Westminster Medical Society on Dec. 7, 1839. An abstract of the paper appeared in the report of the Society in the Lancet, seven days later. I related thirteen cases in detail to the Society, and out of these there was well-marked pericarditis in three cases, and extensive hydrops pericardii, probably unconnected with local inflammation, in two others.
I am not surprised that Dr. Alison is unacquainted with my paper, and I chiefly write to express my dissent from his opinion that pericarditis occurs at an early period in scarlet-fever. I consider that it arises only as a consequence of the renal disease which is apt to follow scarlet-fever. I admit that the kidney is generally disordered during the first few days of the fever, and that its functions are disordered during the rheumatic swellings of the joints which sometimes accompany the eruption, or appear very soon after it; but I am of opinion that percarditis only comes on as a consequence of that congestive disease of the kidneys in which they fail duly to separate the urea from the blood, which disease is never established till a fortnight, and generally not till about three weeks, from the commencement of the fever. Dr. Alison remarks that pericarditis is liable to follow obstructive disease of the kidneys. I have seen it do so independently of scarlet-fever: it occurred only in this manner in the cases related in my paper. I have taken notes of a great number of cases of scarlet-fever, both with and without renal sequalæ, since reading the paper in 1839; these cases tend to confirm the opinion I have expressed respecting pericarditis, and I see nothing in the three cases related by Dr. Alison to induce me to modify that opinion. The subject of the first case was not seen till near death, between two and three months after the fever; in the second case the disease certainly commenced early, but the child, on a previous occasion, had an attack of an inflammatory nature in the left hypochondrium, and Dr. Taylor discovered hypertrophy of the heart only forty-four days after the fever commenced: I therefore conclude that there was disease of the heart in a chronic form, which was rendered acute by the scarlet-fever, as it might have been by any thing which would excite the circulation; and so I am inclined to look on this case as an exception, tending to prove the rule I have expressed. The subject of the remaining case was not seen by Dr. A. till nine weeks after the scarlet-fever, and there is no account by any medical man of the previous illness.
There are many valuable remarks in Dr. Alison's article, and I shall look forward with interest to his promised cases of anasarca following scarlatina.
I am, sir,
Your obedient servant,
John Snow, M.D.
Frith Street, Soho Square,
Feb. 25, 1845.
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14. "On the pathological effects of atmospheres vitiated by carbonic acid gas, and by a diminution of the due proportion of oxygen",
Source: Snow, John. Edinburgh Medical and Surgical Journal1 January 1846, pp. 49-56.
By John Snow, M.D., London
The greater part of the experiments contained in the following paper were related to the Westminster Medical Society on March 30, 1839, and a very brief report of them appeared in the Medical Gazette and the Lancet at the time; but, as the subject to which they relate is of great importance, I have thought it desirable that these experiments should be placed in detail before the profession, and accompanied with some explanations.
There are on record a great number of cases of gradual or slow [49/50] asphyxia from atmospheric air contaminated with carbonic acid gas, but the circumstances under which these accidents occur are always such as to preclude the possibility of analyzing the air producing them. The greatest difference of opinion has existed amongst authors, not only with respect to the amount of deterioration which is fatal or dangerous, but also as to whether carbonic acid is an active poison, or is merely injurious by displacing the atmospheric air; and although the experiments of Collard de Martigny show, in my opinion, the active nature of carbonic acid, they do not show the quantity necessary to produce injury or death; and I know of no experiments on animals, except those I am about to relate, which are calculated to point out the condition of an atmosphere which may or may not be fatal to persons breathing it.
When there is more carbonic acid in the air than the fraction naturally present, there will always be a diminution of the due proportion of oxygen; but this diminution will vary very much with the manner in which the carbonic acid has been produced: if it has been given off from a fermenting vat, or separated from lime or any body with which it was in combination, it becomes added to the air, mixing with it and displacing the nitrogen and oxygen alike. In this case the diminution of the oxygen is equal to twenty-one hundredths of the carbonic acid gas present, or about one-fifth. But if the carbonic acid is the result of the breathing of a number of persons in a limited portion of air, or of the combustion of charcoal or other matter in it, then the carbonic acid gas being formed by union of carbon with the oxygen of the air, the diminution of the oxygen in a given bulk will be always equal to, and in many cases somewhat greater than the amount of carbonic acid present. As an illustration of the above difference in the constitution of the air, I may here remark that a small wax taper is instantly extinguished in air which has been contaminated by respiration till it contains 4 per cent of carbonic acid, whereas 20 parts carbonic acid, or 25 parts nitrogen, require to be added to 100 parts of common air before it will extinguish the flame.
In order to investigate this subject properly, I sought to determine separately the effects of carbonic acid and of a diminished amount of oxygen; and the quantity of air used, in proportion to the size of the animals experimented on, was so great that the result could not be vitiated by the products of their respiration during the experiments.
FIRST DIVISION.-- Experiments undertaken to determine the effects of diminishing the amount of oxygen.
First Experiment.-- Into a large glass vessel, containing 2000 cubic inches of atmospheric air, inverted over water, 70 cubic [50/51] inches of nitric oxide gas were passed, which, combining with part of the oxygen of the air, formed nitrous and nitric acid, which were absorbed by the water. After the entire absorption of these acids, and the volume of the air had been restored to 2000 cubic inches, the composition of this factitious atmosphere was found to be 18 ½ oxygen, 81 ½ nitrogen in every 100 parts, the oxygen being reduced 2 ½ per cent. Into this a white mouse was introduced, and the small quantity of carbonic acid given off from its lungs was absorbed by lime water. It seemed unaffected, and was taken out at the end of five hours.
Second Experiment.-- A sparrow was placed in a factitious atmosphere similar to the last, and at the end of five hours was breathing laboriously. Being left for the night, after seven hours longer, it was found dead.
Third Experiment.-- Into the same vessel 100 cubic inches of nitric acid gas were passed, and an atmosphere was thus formed, in which the oxygen was diminished 3 ½ per cent, being composed of 17 ½ per cent oxygen, and 82 ½ per cent nitrogen. In this a white mouse was placed for ten hours, but seemed unaffected, and was taken out at the end of that time uninjured,
and remained well.
Fourth Experiment.-- A sparrow placed in an atmosphere similarly constituted was taken out at the end of half an hour unaffected, and it continued well.
Fifth Experiment.-- The last experiment was repeated with another sparrow, which was allowed to remain. After a time its breathing became laborious, and it died at the end of six hours. Its blood remained fluid after death, and that in the lungs was of a florid colour. In this, as in all this division of experiments, the small quantity of carbonic acid gas given off from the lungs of the animal was absorbed by lime water.
Sixth Experiment.-- In the same vessel and by the same method 6 per cent of the oxygen were removed, leaving 15 per cent oxygen and 95 per cent nitrogen. A sparrow put into this atmosphere opened its bill and became convulsed at the end of 35 minutes. It was now taken out, but never completely recovered. It died in the course of the following night, and its lungs were found to be soft and gorged with dark fluid blood.
Seventh Experiment.-- A white mouse was placed in a similar atmosphere, and at the end of five hours and three quarters it was insensible, breathing deeply, but very seldom. It was now taken out, and it soon recovered.
Eighth Experiment.-- A green linnet was placed in an atmosphere containing 1 per cent more oxygen than the last, viz. 16.5 per cent
only having been abstracted; and it died in ten minutes.
Ninth Experiment.-- Half of the oxygen having been removed, and the volume restored as before, an atmosphere was formed consisting of 10 ½ per cent oxygen and 89 ½ per cent nitrogen. A white mouse was introduced into this, and it became immediately distressed, breathing deeply and quickly. In five minutes it was nearly exhausted, being no longer able to stand, and evidently on the point of death. It was now taken out, and very soon recovered.
SECOND DIVISION.-- To show the effects of carbonic acid gas, the due amount of oxygen being preserved.
Tenth Experiment.-- Eighty cubic inches of carbonic acid gas and twenty cubic inches of oxygen were passed into the same large vessel, placed over a saturated solution of common salt, and it was filled up with atmospheric air. It then contained a factitious atmosphere constituted as follows,-
21 Oxygen
04 Carbonic acid
75 Nitrogen
100
A linnet was placed in this for eleven hours; it was dull and listless during the experiment, and its respiration was rather deeper than natural; otherwise it was unaffected, and it resumed its usual vivacity directly after the fresh air was admitted to its cage.
Eleventh Experiment.-- 240 cubic inches of carbonic acid, 60 of oxygen, and 1700 of atmospheric air being mixed, an atmosphere was formed containing
21 oxygen
20 carbonic acid
67 nitrogen
in every 100 parts.
A small bird was put in, and its respiration became quicker, deeper, and difficult in less than an hour, and it appeared very uneasy at the end of two hours and a half. When it was left for the night it was in the same state. In the morning it was dead; its limbs were rigid, and the blood in the heart and adjoining large vessels and in the lungs was fluid and dark coloured.
Twelfth Experiment.-- An atmosphere being formed of the following composition,
21 oxygen
20 carbonic acid
59 nitrogen
100
Two birds were put into it. They became greatly disturbed almost immediately, and were taken out at the end of a few minutes, but died shortly afterwards. [52/53] Their feathers, however, got wetted whilst they were being withdrawn, which would diminish their chance of recovery.
Thirteenth Experiment.-- A white mouse was placed in a similar atmosphere. Its respiration became hurried, it became feeble, and died at the end of an hour and a half.
THIRD DIVISION.-- In which there is carbonic acid, with a diminished amount of oxygen.
a. In which the oxygen is diminished only by about one-fifth the amount of the carbonic acid gas present, as in cases where the air is vitiated by a fermenting vat or by a lime kiln.
Fourteenth Experiment.-- Six per cent of carbonic acid were put into the same large vessel, the remaining 94 being atmospheric air; the oxygen was consequently diminished from 21 to very nearly 19 ¾ per cent. Two brown linnets were put into this atmosphere, and they immediately began to breathe deeply, and in ten minutes they opened their bills. They continued to breathe laboriously for four hours and a half, when one of them died. The other one was then taken out, and it commenced to breathe naturally directly afterwards, and remained well till employed in another experiment. The blood of the one that died was of a cherry red colour.
Fifteenth Experiment.-- A white mouse was put into the vessel whilst containing 10 per cent carbonic acid, and 90 common air; the oxygen being thus diminished by two per cent very nearly. The mouse was distressed and breathed deeply from the commencement, and at the end of three hours was removed in a very feeble state, but it recovered directly.
b. In which the diminution of oxygen equals or exceeds the amount of the carbonic acid gas present, as in cases in which the air is vitiated by respiration,
by the combustion of charcoal, or artificial lights.
Sixteenth Experiment.-- A factitious atmosphere was formed, containing 1 ½ per cent of carbonic acid, and in which the oxygen was
diminished by 2 per cent. It was consequently constituted as follows.
01.5 carbonic acid
19.0 oxygen
79.5 nitrogen
100
A linnet was placed in this and allowed to remain for twelve hours. It was not particularly affected during the experiment, and it remained in good health after its removal.
Seventeenth Experiment.-- A candle was allowed to burn in [53/54] the large glass filled with atmospheric air, till on the point of going out. It was removed before the evolution of those poisonous gases which arise from the slow combustion of the tallow in the wick after the flame is extinguished. Consequently, the products of combustion were some carbonic acid and vapour of water, and the composition of the vitiated atmosphere was found to be
03.00 carbonic acid
16.75 oxygen
80.25 nitrogen
100
The air had, therefore, lost 4 ¼ per cent of oxygen, and acquired 3 per cent of carbonic acid very nearly.
A brown linnet was put into this; it began to breathe deeper than natural, and died in 2 ½ hours.
Eighteenth Experiment.-- A wax taper having burnt till it went out for want of sufficient oxygen the remaining air
was found to be composed as follows.
03 carbonic acid
16.5 oxygen
80.5 nitrogen
100
It had consequently lost 4 ½ per cent of oxygen, and acquired 3 per cent of carbonic acid. A white mouse, introduced into this atmosphere, was uneasy from the first, endeavoured to find its way out, breathed laboriously, and after four fours was lying on its side, exhausted and scarcely breathing. It was withdrawn, and recovered after a while.
In this class of birds, the respiratory function is in its highest perfection: the development of animal heat, and the necessity for a constant supply of fresh air are greater than in the rest of the animal kingdom. In the mouse, the respiratory function and the development of caloric are rather low. Contrary to the habit of the small song birds, who live always in the open air, it lives naturally in holes, where the air will necessarily be somewhat vitiated by its own respiration. Accordingly we find that the birds were uniformly sooner distressed and killed than the mice by corresponding atmospheres. The human being, as regards his respiratory function, is placed between the bird and the rodent, and we may therefore conclude that the fatal effects of vitiated atmospheres on him will likewise be intermediate. It must follow, then, that 5 or 6 per cent of carbonic acid cannot exist in the air without danger to life, and that less than half this amount will soon be fatal, when it is formed at the expense of the oxygen of the air, as it is in most cases of accident and suicide.
Whilst these experiments clearly establish the fatal effects of carbonic acid, they disprove some of the arguments from which this gas has hitherto been concluded to be poisonous. It has been said that the illness following exposure to its effects, in cases where the patient was discovered before death, showed its poisonous nature; but in the sixth experiment we have illness and subsequent death after removal from an atmosphere deteriorated by removal of part of its oxygen, whilst no carbonic acid was present; and the chance of recovery after these experiments seemed to depend on the extent and duration of the previous suffering, rather than on the presence or absence of carbonic acid.
It has been argued, that the blood being found florid in the body, was a proof that there was sufficient oxygen in the air, and that, hence, death resulted solely from the carbonic acid. But, in the fifth experiment, the blood in the lungs was florid, when none of this gas was present, and death arose from an insufficiency of oxygen--an insufficiency to maintain life, yet enough to redden the blood.
Carbonic acid gas caused deep and laborious breathing, but in what way it was destructive to life, these experiments do not enable us to state. Its injurious effects seem to depend rather on its physical properties, viz. its density and solubility in the blood, than on any strictly poisonous qualities; and this view is supported by Nysten's experiments of injecting it into the blood-vessels. He sums up the result of his experiments as follows: "Le gas acide carbonique injecté dans le systéme veineux en quantité considérable, mais avec les précautions nécessaries pour ne pas occasionner la distension du cœur pulmonaire, ne donne lieu à d'autre phénomène consécutive notable qu'une foiblesse musculaire qui cesse au bout de quelques
jours" [Recherches de Physiologie et de Chimie Pathologiques, p. 93].
The experiment of Collard de Martigny, in which he was immersed in the gas without breathing it, might seem opposed to this view; but it is to be observed, that he breathed through a long tube, which process, by obliging him to respire part of the same air over and over again, would sufficiently account for all the symptoms he experienced.
The appearance after death in the experiments recorded in this paper were somewhat various, and seemed to depend, rather on the slowness or quickness of dying, than on the constitution of the air causing death. There was no appreciable congestion or other morbid appearance in the brains of those animals which died. Apoplexy has occasionally occurred to human beings under similar circumstances; but the brain of man is a much more complex organ than that of the bird and rodent. Many of these birds sweat profusely during the experiments, breathing laboriously, and placed, as they were, in an atmosphere saturated with moisture.
Naturalists tell us that birds do not perspire; the fact, however, is otherwise; but, under natural circumstances, the perspiration passes off insensibly in the form of vapour, on account of the high temperature of their bodies.
These experiments agree with some points which have been observed in accidents to human beings. For instance, a contaminated atmosphere has been known to prove fatal, though it produced no inconvenience at first. Now, in the majority of these experiments, the animals were apparently not affected till after a longer or shorter time. It has been observed, that air contaminated with carbonic acid may be dangerous, although a candle will continue to burn in it, and such was the state of the air in the fourteenth and fifteenth experiment.
Professor Graham suggested a plan, which has been published in the reports of the Royal Humane Society, of absorbing the carbonic acid gas remaining after the explosion of fire-damp in coal mines, by means of inhaling the air through a cushion filled with a mixture of slaked lime and pounded sulphate of soda. But we have seen that the carbonic acid is not the only cause of injury; and since, from the constitution of fire-damp, the loss of oxygen by its explosion will, in every instance, be at least twice as great as the carbonic acid which is added, this ingenious contrivance could remove but a small part of the vitiation, and, by giving a false idea of security, would be likely to increase, instead of diminishing accidents.
Professor Graham evidently partakes of an error, which, I believe, is pretty general in the profession, viz. that the whole, or nearly the whole, of the oxygen of the air is available for respiration. He says, "In many cases the oxygen of the air is not exhausted by the explosion, although, from the presence of 5 or 10 per cent of carbonic acid, it is rendered irrespirable." Now, if but 5 per cent of carbonic acid were present after the explosion, half the oxygen of the air would be gone, and the other half would not support life for five minutes; consequently, after the absorption of the carbonic acid, the residual air would be instantly fatal.
The amount of oxygen cannot be reduced by any notable amount without danger. I mean the amount in proportion to the nitrogen; for the amount in a given space may be greatly reduced, provided the nitrogen be reduced pari passu, since, on high mountains, persons suffer only a little inconvenience, when the quantity of oxygen in a given space is reduced below what would be quickly fatal, and what would admit of the combustion of no ordinary materials, if the full amount of nitrogen were present.
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15. "On the use of the term 'Allopathy'",
Source: Snow, John. Lancet 1, 21 February 1846, p. 229 [Letter to Ed.].
To the Editor of the Lancet
Sir,-I regret to see, in a late leading article, that you (unguardedly, as I believe) adopt the nickname "allopathy," which the homœopathists have tried to impose on the profession; for there is nothing which would, in my opinion, tend so much to prolong the brief day of the fatal and extravagant system of homœopathy as an acquiescence in the term allopathy, so inapplicable to the science of medicine. Its adoption would greatly increase the importance of the framers of both terms, and would assist to hide from the public the fact that their practice is opposed by the accumulated experience of all the nations, not only that of medical men, but of the people at large. A person knowing but little of medical science, (and this must ever be the case of the greater number of patients,) would say--allopathy--homœopathy--well, doctors disagree, I have tried one pathy, now I'll try the other.
Medical men do not endeavour to cure disease by producing others of an opposite kind; they do not always oppose the actions which are going on in illness, or, as a general rule, adopt measures which would produce in a healthy person a state opposite to that which exists in the disease under treatment; consequently, I conclude that the word allopathy must be admitted to be a misnomer. An erroneous term is always injurious, even amongst the scientific, but the reception of this would be especially so to the public, who must be guided in the choice of medical men and medical systems by general impressions and mere report, and not by correct data on which they can reason; and I can conceive nothing that would more rejoice the homeopathists than the general adoption of a designation, which would imply, not that they were at variance with the accumulated knowledge of all the world on therapeutics, but merely with the opinion of an opposite party.
I remain, Sir, your obedient servant,
John Snow, M.D.
London, February, 1846.
*** We cordially concur with the orthodox remarks of Dr. Snow, and feel with him that the less the term allopathy is used by
professional men, the better.--Ed. L.
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