Physiological Researches on Life and Death

by Xavier Bichat

FOOTNOTES:

[100] When the diaphragm is ruptured, a sudden cessation of the functions is not always the result of this accident. Patients have been known to survive many days, and the cause of death has only been ascertained by examining the body.

The intercostal muscles are, in this case, the sole agents of respiration, which becomes nearly analogous to that of birds or to that of animals with red and cold blood, who are destitute of the septum between the thorax and abdomen.[101]

Lieutaud cites various ruptures of the diaphragm, produced by other causes than external injuries. Diemerbroech has seen this muscle wanting in an infant who still lived to the age of seven years.

[101] When from any cause, the diaphragm cannot contract, the enlargement of the thorax is effected solely by the elevation of the ribs, and as this motion is then very evident, we can then appreciate better the influence the intercostal muscles have in its production in ordinary respiration. Haller, as is well known, supposed that the first rib was almost immoveable, and that the muscles in the first intercostal space, took it as their fixed point to elevate the second. This second rib, in its turn, served as a fixed point to elevate the third, and thus on to the last rib. But if we observe the mechanical phenomena of respiration when the diaphragm does not contract, as is the case in diaphragmatic pleurisy, we see that the first rib is far from being immoveable. Now, we cannot conceive how the intercostals which are attached to its inferior part, can, by contracting, assist in raising it. Besides, in order to elevate the ribs, a very great resistance must be overcome, and the intercostal muscles are too slender to induce us to suppose that they are capable of effecting it. The principal agents of this motion then are the anterior and posterior scaleni, which are distinctly seen to contract in great inspirations, the supra-costales and the muscles of the neck which attach it to the sternum. We ought to add to these a muscle, to which this use has never before been attributed; I mean the diaphragm. This muscle in fact in its contraction tends to become flat, from being concave as it is in inspiration. Now, its middle part in depressing the abdominal viscera experiences a certain resistance, and takes, as it were, from them a fixed point, by means of which it elevates the base of the thorax to which its circumference is attached.

[102] Asphyxia is not always the cause of death in those who are hung, there is sometimes connected with it a more efficient cause, which consists in the compression of the spinal marrow. This was formerly very often observed in those who had been executed, because the executioner in throwing them off gave a rotatory motion to the body which produced the luxation of the first vertebra on the second.

[103] By injecting into the veins different irrespirable gases, Nysten has been able to distinguish the effects which result from the deleterious properties of the gases from those which arise from the alteration of respiration from a want of atmospheric air.

Thus among the elastic fluids which he tried, he found sulphuretted hydrogen, the deutoxide of azote, chlorine and ammoniacal gas eminently deleterious; for introduced in sufficient quantity into the animal economy they uniformly cause death, whilst others, such as oxygen, azote, hydrogen, carburetted hydrogen, carbonic acid, oxide of carbon, and protoxide of azote do not produce death when introduced into the lungs, except by excluding the only mixture, that can support respiration; in no other way do they occasion death, at least in a sudden manner. If however, they are thrown quickly into the blood vessels, they cause death, but it is mechanically and in the same way as atmospheric air would do it. It should also be observed that these different gases do not all act in the same way when they are introduced into the lungs; the gaseous oxide of carbon destroys animals much quicker than azote or the protoxide of azote. They die also quicker in the proto-phosphuretted hydrogen, and even in the carbonic acid gas. There are also in the action of deleterious gases certain anomalies which have not hitherto been explained. Nysten injected, at three injections, into the veins of a dog of middle size thirty centimetres of sulphuretted hydrogen. The animal after the first injection, was agitated, and made powerful inspirations; the second produced convulsive motions and the third apparent death; but the next day he was entirely well. Now a less quantity of sulphuretted hydrogen carried into the organs of respiration and mixed with five or six hundred times its volume of air, would infallibly destroy the animal.

[104] The composition of some of these vapours is better known at the present day; but there are others in which our means of analysis have been unable to detect the deleterious principle; thus in the malaria, which has depopulated the country in the neighbourhood of Rome, our chemists have as yet only found as constant elements, those which enter into the composition of atmospheric air.

[105] It appears from the experiments of M. Desormes that the contact of sulphuretted hydrogen on the skin of an animal is immediately fatal.

[106] We know that fine injections pass from the branches of the pulmonary artery into the divisions of the bronchia; and that even water, when pushed into the trachea, will return, at least a small quantity of it, by the pulmonary veins and arteries.

Bichat thought that the gases absorbed in the lungs must pass through the mucous membrane; but this is not the case unless absorption takes place at the time they are in the bronchia, for the mucous membrane which lines the air-tubes does not extend into each bronchial lobule.

[107] This fact, frequently confirmed in my experiments, is not always the same in man. We often see emphysema produced by violent efforts of respiration, efforts which have forced into the cellular organ the air contained in the lungs. Now, if the passage of the air in the blood preceded or even accompanied its introduction into the neighbouring cells of the bronchia, all these cases of emphysema would be necessarily fatal, and even in a sudden manner, since, from what has been said before, the contact of the air on the brain, to which the circulation would carry it, would inevitably interrupt the functions of this organ.

Yet we see that emphysema is often cured, or does not produce death for a length of time.[108] I saw, at the Hotel Dieu, an air tumour, suddenly appear in the axilla, from the violent efforts of the patient to prevent respiration, whilst Desault reduced an old luxation. In a few days this tumour disappeared without producing any inconvenience. We find, in the Memoirs of the Academy of Surgery and in Treatises on Operations, various examples of emphysema produced by powerful agitations of the thorax, and in consequence of the introduction of a foreign body into the wind-pipe; emphysema, with which the patients have lived many days, and from which even they have recovered.

There is then no doubt, that often in man the air passes from the lungs into the cellular texture, without entering the arterial system. My experiments on animals have not been exactly analogous to what happens from the introduction of a foreign body, when a part of the air enters and goes out. It is then probable that from a cause precisely similar would arise also the same effect in animals.

And vice versa, the passage of the air in the blood-vessels sometimes takes place in man, without the infiltration of the cellular organ; then the death is sudden.

A fisherman, subject to colick, was suddenly seized with it in his boat; the abdomen swelled, the respiration became painful and the patient died almost instantaneously. Morgagni opened the body the next day, and found the vessels full of air. Pechlin also says he saw a man die suddenly in great distress and with a hurried respiration, and he afterwards found a large quantity of air in the heart and in the large vessels.

I have dissected many bodies, in which, before death there had been a sanguineous congestion in the exterior capillary system of the face, the neck and even of the thorax. This system exhibited a remarkable engorgement and lividity in all its parts, and I have found in opening the arteries and veins, in those of the neck and head especially, a frothy blood, mixed with bubbles of air. I learnt that one of these subjects died suddenly with a convulsive affection of the pectoral muscles; I have no information respecting the others. Besides, all who have had much to do with dissecting rooms, must have seen bodies of this kind, which very soon become putrid and emit an insupportable odour. They have observed also that the air in the vessels existed previous to the putrefaction.

I suspect that in all these cases death has been produced by the sudden passage of air from the lungs into the blood, which has afterwards carried it to the brain; nearly like what I have said takes place, when, in a living animal, we force much air towards the lungs, and thus drive this fluid into the vascular system.

By considering these phenomena in connexion with the remarks presented above on death from the injection of air into the veins, the opinion I have advanced, will I think, be admitted, and it is besides the opinion of many other physicians. Many experiments have already been made on the dead body relative to this point. Morgagni has presented them in detail; but it is on the living that we must observe the passage of the air into the blood in order to deduce consequences which shall bear on the subject on which we are treating. We know in fact what is the influence of death on the permeability of the parts.

[108] I saw, in a little girl of seven or eight years of age, an emphysema which occurred in a paroxysm of coughing, and which extended to the thorax, the abdomen and the superior part of the thighs; the swelling of the neck was so considerable, that at the moment I was called suffocation was imminent. I made, in the skin above the sternum, an opening, which very quickly produced an evacuation of the air. In five or six days, though the hooping cough continued, this little patient was entirely cured of the emphysema, which had been very near destroying her. It did not appear to me that the lungs had participated at all in the general emphysema.

[109] The above experiments explain the manner in which emphysema is produced from any very violent exertion of the muscles of the chest.

[CHAPTER X.]
OF THE INFLUENCE OF THE DEATH OF THE BRAIN OVER THAT OF THE LUNGS.

As soon as the human brain ceases to act, the functions of the lungs are suddenly interrupted; this phenomenon, which is constantly observed in the red and warm-blooded animals, can happen only in two ways. 1st, Because the action of the brain, is directly necessary to that of the lungs, or 2dly, Because the latter receives from the former, an indirect influence by means of the intercostal muscles and diaphragm, an influence, which ceases with the activity of the cerebral mass. Let us try to determine which of these two modes is that of nature.

I. Is it directly that the lungs cease to act upon the death of the brain?

I shall have proved that the death of the brain, is not immediately the occasion of that of the lungs, if I can determine that there is no immediate influence exercised by the first, upon the second of these organs, now, this essential principle may be easily demonstrated by experiment.

The brain can exercise an immediate influence on the lungs, only by means of the par vagum or the great sympathetic nerve, the only nerves, which according to the common opinion, establish a communication between the two organs (an opinion however which is erroneous, as the great sympathetic is only an agent of communication between the organs and the ganglions of the system.) Now 1st, The influence which is derived by the lungs from the par vagum, is not actually necessary for them to act. The following experiments will show the truth of this assertion.

1st, Irritate the par vagum on one or both sides, and the respiration of the animal will be somewhat quickened; but such appearance is no proof of an immediate influence, for any wound of the neck, or any wound whatever, provided that it be the occasion of considerable pain, will be the cause of a similar phenomenon.

2dly, Cut one of the nerves, and the respiration will be at once affected, as when the nerve is irritated; but as soon as the pain ceases, the embarrassment of the lungs will disappear; and at the end of four and twenty hours, the phenomena of life be concatenated with their accustomed regularity.

3dly, Divide these nerves on both sides. In this case the breathing will be much more precipitated, and will not return to its ordinary state, as in the preceding experiment; it continues laborious for four or five days, and the animal perishes.[110]

From the two latter experiments it follows, that the par vagum is indeed necessary to the phenomena of respiration, and that the brain must exercise, of course, an influence over this function, but at the same time, it may be seen, that without the immediate influence of the brain, the lungs will continue in play, and consequently that the interruption of such influence, as when the brain is injured, will not be an immediate obstacle to the continuation of the pulmonary actions.

The question whether the functions of the lungs are more immediately connected with the influence derived from the ganglions, may be decided by the following facts.

1st, If on the one and the other side of the neck, the nervous thread be cut, which is usually regarded as the trunk of the great sympathetic, there follows little or no alteration in the phenomena of respiration.

2dly, If the par vagum and the great sympathetic be divided at the same time on both sides of the neck, the animal will die after a certain time, and much in the same way, as when only the par vagum is divided.

3dly, When we divide the sympathetic nerve in the neck, we do not deprive the lungs of the nerves which come from the first thoracic ganglion; now these nerves may contribute to keep up the action of the lungs, since, as I have said, each ganglion is a nervous centre, capable of emitting its own peculiar irradiations, independently of the other centres, with which it communicates.

But whether the nerves, which are derived from the first thoracic ganglion, do really assist the functions of the lungs, I have not been able to ascertain by experiments on the nerves themselves, for such is the position of the first thoracic ganglion in most animals, that it cannot be taken away without doing so much injury to the parts as would kill the creature, or throw it into such agitation, as wholly to confound the phenomena of which we are in search, with those of a general distress and trouble. From analogy, however, and from the destruction of other ganglions, by which the internal organs are supplied, we should not have a right to suppose that the lungs would cease to act, when the ganglion in question is destroyed.

Besides, the following reasons appear to me to prove unquestionably, the principle which I advance. If great lesions of the brain have the effect of suddenly interrupting respiration, because this organ can no longer influence the lungs by means of the nerves, which come from the first thoracic ganglion, it is evident that if all communication between the brain and this ganglion be taken away, such influence must cease, and respiration be suspended; but if we divide, as Cruikshanks has done, the spinal marrow on a level with the last of the cervical vertebræ, the animal will continue to live and breathe for a length of time, notwithstanding the want of communication between the brain and the lungs, by means of the first thoracic ganglion. From the above experiments, we may conclude, that the brain does not exercise any direct and actual influence over the lungs, and consequently that other causes must be sought for, if we mean to account for that sudden and instantaneous cessation of the functions of the latter of these organs, when those of the former are suspended.

There exists, notwithstanding, a phenomenon which seems to cast some doubt upon the conclusion which I have deduced, and in the principle which it establishes. I speak of the sudden difficulty of respiration, and that impeded circulation which are occasioned by violent pain. This distress appears to indicate that the heart and the lungs are dependent immediately upon the brain; for the distress is in the brain, say the greater number of authors, and the affection of the heart and lungs, a consequence of the reaction of the brain; but here let it be remembered, that almost all pain is made up, first of sensation, and secondly of some emotion, passion or affection.[111] Now as I have proved at length, in the former part of this work, all passion and emotion have their seat in the internal viscera, and thus it will appear, that the trouble which in such case is felt in the heart and lungs, does not depend upon the brain for its cause, but is the immediate effect of the passion, or emotion, which accompanies the sensation. The following considerations will bear me out in this conclusion.

1st, In many instances the dyspnœa and impeded circulation, precede the pain. Examine the thorax, and place your hand upon the heart of a man about to undergo an operation, and you will be easily convinced of this truth.

2dly, There is sometimes a manifest disproportion between the sensation of pain, and the distress which is experienced about the heart, and in breathing. I have known the operation of cutting away the prepuce immediately fatal. Now in this case, it surely could not be pain which killed the man.

3dly, There are many persons who are capable of supporting violent pain, with resolution. Place your hand upon the heart of such persons, and no agitation whatever will be felt there. Nevertheless, their perception of pain must be what it is in other persons.

4thly, In the course of an operation, we are not to judge of the patient’s state of mind, from his cries, or silence. This sign is very deceitful; because a man may be sufficiently master of himself to overpower the influence of his internal organs. We must examine the heart and lungs; their functions, if I may allow myself the expression, are the thermometer of the affections of the mind. It is not without reason, that the actor who plays the part of a courageous man, takes hold upon the hand of him whom he wishes to set at ease, and lays it on his heart. The exterior movements of the passions, are not a fair criterion of the inward feelings of the individual, for these movements may be feigned as well as real: feigned if they originate in the brain: real if they have their sources in the heart;—in the first case voluntary, in the second involuntary. Touch the pulse of the angry man, if you wish to know whether he really is in anger. When I see a woman weeping or convulsed at any distressing news, and find her pulse in its natural state, I know what to judge of her affliction.—On the contrary, if her grief be concentrated, but her heart beat strongly, or her pulse have been suddenly depressed, I know that she feigns a calm which she does not feel. To judge correctly, we must always compare the external movement with the state of the internal organs. There could be no deceit, were it possible to distinguish the involuntary movements produced in a state of passion, by the action of the heart upon the brain, and then by the reaction of the brain upon the muscles, from the voluntary movements which are occasioned by the simple action of the brain upon the locomotive system.

However strong may be the pain which has been the occasion of the dyspnœa, and impeded circulation, of which we have been speaking, this dyspnœa and distress about the precordia, will cease, provided only that the pain be continued. Nevertheless, if the reaction of the brain were the real cause of the distress in question, the contrary should be the case; for the continuation of the affection of the brain, should continue also to cause its re-action. But here the effect of habit is evident, though the pain subsists; the brain indeed continues to be affected, but the internal organs cease to be so. It may be easily perceived, that I am not here speaking of those cases, where the action of the heart and lungs has been deeply troubled by the effect of pain.

To the above considerations I might add many others, with the view of proving, 1st, That although the brain be the seat of the pain, it is not the source of those affections of the internal organs, which are occasioned by such pain; 2dly, That these affections depend upon an emotion, which is absolutely distinct from sensation of whatever kind, both in its nature and effects.

II. Is it indirectly that the lungs cease to act upon the death of the brain?

Since the death of the lungs, upon the cessation of the cerebral action, is not direct, there must exist between the brain and the lungs, some intermediate agents, the cessation of whose functions, occasion the cessation of those of the lungs. These agents are the diaphragm, and intercostal muscles; for they depend immediately upon the brain by means of the nerves, which they receive from it, and consequently become paralytic on the death of the brain; the following experiments are a proof of the fact.[112]

1st, Cruikshanks divided the spinal marrow of a dog between the last cervical, and the first dorsal vertebræ. The intercostal muscles accordingly were immediately paralyzed, and the breathing of the animal continued to be made by the diaphragm only, which receives the phrenic nerve from a point above the section. In this experiment, it is easy to judge of the strong action of the diaphragm, by that of the abdominal muscles.

2dly, If the phrenic nerves only be divided, the diaphragm becomes immoveable, and then the respiration of the animal is effected by the intercostal muscles only.

3dly, After the two preceding experiments, the animal will live for a considerable time, but if the phrenic nerves, and the spinal marrow, towards the end of the neck, be divided at the same time, or what comes to the same thing, if the spinal marrow be cut above the origin of the phrenic nerves, then all communication between the brain and the active agents of respiration is cut off, and death follows of course.

4thly, I have frequently observed, that half an inch of difference in the place where the spinal marrow is divided, produces such a difference in its consequences, that in the one case the death is sudden, and supervenes in the other only, after an interval of fifteen or twenty hours. In dissecting the carcases of animals killed in this manner, I have constantly observed that the difference depended always upon the circumstance, of the phrenic nerve being cut or not.

From these experiments then it is evident, that respiration ceases on a sudden, and in the following manner, in all lesions of that part of the nervous system, which is placed above the origin of the phrenic nerves. 1st, There is an interruption of action in the voluntary nerves, which are placed below the point of lesion, and consequently in the phrenic and intercostal nerves. 2dly, A paralysis of almost all the muscles of the animal life, and particularly of the diaphragm and intercostal muscles. 3dly, A cessation of the mechanical phenomena of respiration. 4thly, A suspension of the chemical phenomena of respiration. The interruption of all these movements, is as rapid as their concatenation is prompt, in the natural order.

It is thus that those persons perish, who experience any great lesion of the spinal marrow, between the brain and the origin of the phrenic nerves. Physicians have been very much embarrassed, in fixing with precision the spot, when a wound of the medulla ceases to be mortal; from what I have advanced, the limit is easily assigned.[113] From the same causes, concussion, and compression of the brain, are also fatal.

We should observe notwithstanding, that these different causes of death, may act with various degrees of intensity. If they act but feebly, they affect the intellectual functions only, for these functions are always the first to be altered, in all lesions of the brain however small. If the lesion be greater, the affection extends to the muscles of the limbs, and convulsion or palsy ensue. Lastly, if the lesion be very great, the whole of the muscles of the animal life, the intercostals and diaphragm, as well as the others, are paralyzed, and death follows.

We now can reply to the question proposed at the beginning of this section, and affirm that the death of the lungs is occasioned indirectly, by the death of the brain.

It follows also, from the principles which are above established, that respiration is a mixed function, a function placed as it were between the two lives, to which it serves as a point of contact, belonging to the animal life by its mechanical functions, and to the organic life, by its chemical functions; and hence we have the reason no doubt, why the existence of the lungs is as much connected with that of the brain, as with that of the heart.

It may be observed in the series of animals, that in proportion as the organization of the brain is straitened, a number of the phenomena of respiration also are lost. In birds, and the mammalia, this function as well as the brain, is much more developed than it is in the classes of fish and reptiles. It is known, that the nervous system of those animals which breathe by tracheæ, is less perfect than in those which breathe by lungs; and that in those, where there is no nervous system, that of respiration disappears also.

In general, there is a reciprocal relation between the brain and the lungs, especially in birds and the mammalia. The first of these occasions the action of the second, by raising the ribs and favouring the entrance of air into the bronchiæ; the second also keeps up the activity of the first, by means of the red blood which it sends thither.

It would be an interesting speculation to inquire into the relation of the nervous system with that of respiration in the class of insects, for as they receive the air by points, which open externally, there seems to be no mechanical action in the process of their breathing, and thus the function appears with them to belong entirely to the organic life.