Physiological Researches on Life and Death

by Xavier Bichat

FOOTNOTES:

[94] It is not possible to remove by this means a great portion of air contained in the lungs, for the last ramifications of the air-tubes being flexible, their parietes soon come in contact, and thus oppose the exit of the air contained in the bronchial cells.

[95] These observations have been made on the great mammalia, and there has not been remarked any difference of colour.

[96] The difference that is remarked in the results of this experiment, compared with that in which the venous blood is introduced by means of a syringe, arises probably from this, that in the first the blood that is forced into the artery has already begun to coagulate.

[97] The deficiency of cutaneous exhalation in the last moments of life may contribute a little perhaps to the preservation of animal heat; but we have shown that there are other more powerful causes for this phenomenon. This deficiency of exhalation united to the inaction of the secretory organs, in the very short period in which the black blood runs in the arteries is an altogether insufficient cause to explain the abundance of blood that is found in the vessels of those who have died of asphyxia.

[98] This is not an uniform fact, and it is even very common to find, in persons who have been hung, the bladder completely empty.

[99] The moment respiration ceases, and the source of heat is consequently cut off, it is not astonishing that an animal body should become cold quicker in water then in a much less dense fluid, like the air. It should also be remarked that the water, on account of the evaporation that takes place on its surface, has almost always a temperature below that of the surrounding air.

[CHAPTER IX.]
OF THE INFLUENCE OF THE DEATH OF THE LUNGS, OVER THE GENERAL DEATH OF THE BODY.

In recapitulating what has been said in the preceding chapters, with respect to the influence of the lungs over the heart, the brain, and all the organs, it is an easy matter to form an idea of the successive termination of the whole of the functions, when the phenomena of respiration are suspended either mechanically or chemically.

The following is the manner in which death supervenes, when the mechanical phenomena of the lungs are interrupted, either from the causes mentioned in the 5th chapter, or from similar ones, such as the rupture of the diaphragm, which I have twice had occasion to observe,[100] or from a fracture of a great number of the ribs, or the sternum.

1st. The mechanical functions of the lungs cease. 2dly. The chemical functions of the lungs cease also. 3dly. The cerebral actions are put an end to. 4thly. The animal life is interrupted. 5thly. The general circulation is interrupted. 6thly. The capillary circulation is interrupted.

The phenomena of death, are differently concatenated, when they begin by the suspension of the chemical functions of the lungs: which may happen, 1st, From breathing in a vacuum; 2dly, From the obliteration of the passage of the trachea, by foreign substances introduced into it, or by tumour from without, or strangulation, accumulation of fluid in the air cells, &c.; 3dly, From different inflammatory affections, schirrhi, &c. of the cavities of the mouth or throat. 5thly, From want of respirable air, as on the summit of high mountains. 6thly, From the introduction into the air cells of non-respirable gases, &c. &c. In all these cases, the following is the order of the phenomena of death.

1st. The chemical functions of the lungs are suspended. 2dly. The functions of the brain are interrupted. 3dly. Sensation, locomotion, the voice, the mechanical phenomena of respiration cease. 4thly. The action of the heart, together with the general circulation is annihilated. 5thly. The capillary circulation is put an end to, together with the processes of secretion, exhalation, absorption, and digestion. 6thly. The animal heat of the system dies away.

I. Remarks upon the differences of asphyxiæ.

The influence of the black blood as I have said, is always the great agent in this double sort of death, but it is not the only one: if that were the case, the phenomena of all the asphyxiæ would be alike. It is true that in every sort of asphyxia, the black blood ceases to become red blood, and circulates in the arteries, such as it is in the veins; but notwithstanding the uniformity of this phenomenon, there can be nothing more varied, than the symptoms and progress of these accidents. In some of them, death is long in taking place; in others, almost instantaneous: the phenomena developed in the last moments of existence, are alike in none of them. The state of the organs, and that of the powers which they preserve after death, are as various.

1st, Asphyxia varies with respect to its duration; in sulphurated hydrogenous gas, in nitrous gas, and certain vapours arising from privies and sewers, it is quick in taking place. In carbonic acid gas, azote, in pure hydrogen, water, and a vacuum, its progress is slower.

2dly, Asphyxia varies with respect to its attendant phenomena. At times, the animal is violently agitated and suddenly convulsed; at others, it appears to lose its powers gradually; to pass into a state of sleep, and from sleep into a state of death. In comparing the numerous effects arising from the vapours of sewers, from those of charcoal, from the different gases, from drowning, and other causes of asphyxia, we find them almost as various, as the causes themselves.

3dly, The phenomena which make their appearance after death, are as variable. Compare the cold and frozen carcase of a drowned man, with the remains of one who has been suffocated. Read the result of the different experiments of the Institute, upon the affections of the galvanic fluid in the different asphyxiæ; examine Halle’s detail of the symptoms which accompany the mephitism of sewers; approximate the numerous observations, which are scattered about in the works of Portal, Louis, Haller, Troja, Pechlin, Bartholin, and Morgagni; repeat the most common experiments on the submersion, strangulation, and suffocation of animals; and you will observe the greatest difference in all these sorts of asphyxia, they are each of them characterized, by a peculiar state of the bodies of the animals, which have been submitted to the experiment.

To inquire into the causes of such differences, we must first divide the asphyxiæ into two classes. 1st, Into those which happen from the simple want of respirable air, and 2dly, Into those, where to this first cause is joined also that of the introduction of some deleterious substance into the lungs.

In the first class, the immediate cause of death, appears to be the simple presence of the black blood, in the various parts of the body, the general effect of which is always the same, in whatever manner produced; accordingly, the attendant symptoms and secondary results of all these sorts of death, are nearly alike, their duration the same, and if it varies, it varies only in consequence of the more or less complete interruption of the passage of air into the lungs.

This variety in the duration and intensity of the asphyxiating cause, may nevertheless occasion some variety in the symptoms also; such as a greater or less lividity and swelling of the face, a more or less considerable embarrassment of the lungs; but all these differences indicate only so many modifications of the cause, 1st, A man who is hanged, does not die as a man who is suffocated by an inflammatory tumour, or a pea or bean which perchance may have fallen into the trachea.[102] 2dly, An animal will perish much more slowly under a vessel of air, than when the trachea is tied. 3dly, The symptoms of asphyxia, when occasioned by a great rarefaction of air, or by a suffocating heat, are much less slowly produced, than where the cavity of the lungs is opened.

In all these cases the cause of death, namely the absence of red blood in the arterial system, is simple and unique, but according to the greater or less oxygenation of the venous blood, will be the appearances after death, for the longer the process of asphyxia endures, the less irritability will there be found in the system.

But if the cause of asphyxia, have been the introduction of some deleterious fluid into the lungs, then the variety of the symptoms will depend upon the difference in the nature of the fluid. In these cases the cause is of two kinds: 1st, There is no red blood in the system. 2dly, A pernicious fluid is present in the system. All the gases however do not act as deleterious substances: in pure hydrogen for instance, the animal perishes only as it would from the want of respirable air.

But when a man in descending into a common sewer, into a cellar, or into any place where putrid matters are accumulated, falls into asphyxia at the moment when he inspires their exhalations, and when such state is attended with convulsive movements and extreme agitation, then indeed, there must be something more in the cause of his death, than a simple suspension of the chemical functions of the lungs.

In fact, together with the mephitic vapour, there continues to enter into the lungs a sufficient quantity of air to keep up life and its different functions. 2dly, Supposing even that the quantity of mephitic air were such as to leave no place for the entrance of respirable air, still the death ensuing should only be gradual, without agitation and convulsion, were it occasioned only by the absence of such air: now the very different way in which it supervenes, very evidently indicates the action of a deleterious substance, upon the animal œconomy.[103]

These two causes then act together, in those asphyxiæ which are produced by certain gases, sometimes the one predominates, sometimes the other. If the deleterious substance be violent, it kills before the action of the black blood can have produced much effect, if weak, it is the black blood, which is principally the cause of death.

The asphyxiæ then, which are produced by the gases, differ only, in consequence of the nature of the deleterious substance, which varies ad infinitum. In some of the aeriform fluids indeed it is supposed to be known, but in the greater number of them it is not so:[104] I shall notice therefore in a general way the effects, which result from the action of the deleterious substance, remarking at the same time, that the symptoms by which they are displayed, are strongly or weakly marked, according to the age and temperament of the individual.

Deleterious substances introduced into the lungs, together with the mephitic vapours of which they form a part, can act only in two ways. 1st, By affecting the nerves of the lungs, which re-act on the brain. 2dly, By passing into the blood, and exercising their influence, by means of the circulation on the various organs of the system.

I can easily believe that the simple action of such a substance on the nerves of the lungs, may have a very marked effect on the economy, and be capable of troubling the functions of the system very sensibly; much indeed in the same way as with some individuals a mere odour, or the sight of a hideous object, will occasion syncope, in the same way that an irritating enema will suddenly awake the system into life, or the introduction of certain substances within the stomach, will be felt throughout the body, before such substances can have passed into the circulatory torrent. We meet at every moment with examples of these very remarkable phenomena, produced by the simple impressions of foreign bodies on the mucous surfaces; I cannot deny that deleterious substances may act in the same way upon the nerves of the lungs, though we must not exaggerate the sphere of this mode of action.[105]

In fact, I am not acquainted with any one example, where the contact of a deleterious substance with a mucous membrane, has been the sudden cause of death. It may indeed be productive of such effect after a certain time, but never at the moment of its action; nevertheless, in those asphyxiæ which are produced by mephitic vapour, so rapidly does death come on, that the black blood can scarcely have had the time to exert its influence upon the body. The principal cause of the cessation of the functions is manifestly the action of the pernicious substance.

These considerations, then, incline me to believe, that these substances pass into the blood through the lungs, and that in circulating with the blood they carry to the organs the immediate cause of their death. Such passage into the blood has already been suspected by many physicians; the truth of the fact appears to be indubitably proved by the following reflections.

1st, It can hardly be doubted, that the poison of the viper and many other venomous animals, and that the saliva of rabid animals, pass into the system of the blood, and are taken up either by the veins or the lymphatics.

2dly, It appears to be very certain, that a portion of the atmospheric air is actually absorbed through the mucous membrane of the lungs itself, and not by means of the absorbent system. Now, if this be the case, I know not what should hinder the passage of mephitic vapour in the same way.[106] We are not sufficiently acquainted with the limits of the particular sensibility of the membrane of the air cells, to say that it cannot give a passage to such vapour.

3dly, The respiration of an air which has been charged with the exhalations arising from oil of turpentine, communicate a particular smell to the urine. It is thus that this fluid is affected from the residence of the persons in a newly varnished room. In this case it is evidently by the lungs in part, that the odoriferous fluid has its passage into the blood, and so on to the kidneys. In fact, I have often assured myself by breathing out of a bottle through a tube, air so charged (in which case it could not act on the cutaneous surface) that the smell of the urine undergoes a change. If, then, the lungs will admit a variety of substances, which do not enter into the composition of respirable air, for what reason should they not admit the mephitic vapour of mines and subterraneous places.

4thly, The respiration of humid air produces dropsy. The extent of the fact has been exaggerated, indeed, but the fact itself is true. It proves, that an aqueous fluid may pass into the blood, and consequently that other substances may pass into it also.

5thly, If an animal be asphyxiated in sulphurated hydrogenous gas, and a plate of metal some time after its death be placed under one of its muscles, the surface of the plate contiguous to the muscle, will be sensibly sulphurated. The foreign principle, then, which is here united with the hydrogen, must have been introduced into the circulatory torrent by the lungs, and have penetrated with the blood into all the parts. The deputies of the Institute have observed this phenomenon in their experiments. I have made a similar remark in asphyxiating animals with nitrous gas. A phenomenon of the same nature accompanies the exhibition of mercury.

From the above, we have nearly a right to conclude, that the different deleterious substances of which the gases are the vehicles, do actually pass into the blood, and so affect the organs. Of this matter, however, I shall adduce some further proofs.

I have ascertained by a number of experiments, that atmospheric air, or any other aeriform fluid, may be made to pass into the blood without alteration.

Divide the trachea of a dog, inject the air-cells strongly with common air, and continue to retain it in the lungs. The animal will immediately discover signs of great distress and agitation; if an artery now be opened, the blood will be emitted in a frothy state.

If hydrogen have been employed, it may easily be ascertained that the nature of the fluid is unchanged, by placing a candle over the bubbles which are disengaged.

When the blood for the space of thirty seconds has flowed in this state, the animal life of the creature will be finished, and death ensue, with all the symptoms which accompany the insufflation of air into the black-blooded system of vessels. The re-admission of air into the lungs, will have no effect in restoring the animal to life, for as soon as frothy blood can flow from any one of the arteries, it must already have affected the brain with its pernicious influence.

In this case it may be perceived, that the causes of death are the same as those which proceed from the insufflation of air into a vein. In the one instance the air passes at once from the lungs into the arterial system. In the other, from the veins across the lungs and then into the arteries.

When we open the bodies of animals, which have been killed in these experiments, the whole apparatus of the red-blooded vascular system, is found to be filled with air bubbles of various sizes. In some circumstances, the blood will be transmitted in the same state into the general capillary system, and from thence into the veins; in others it will be stopped in the capillary system, and in such cases, though the circulation may have continued for some time after the suspension of the animal life, not a single particle of air will be discovered in the veins.

In these experiments which I have frequently repeated, I have never found that the least fissure has been made in the bronchiæ; nevertheless, I confess that it is difficult to say, whether this be so in their last ramifications. The following phenomenon, however, may throw some light upon the subject; for as often as air is pushed into the lungs with great violence, there will be produced an emphysema of the breast, or neck, from the infiltration of this fluid among the cellular texture, in addition to its passage into the blood. But if the impulse be moderate, and the quantity of air injected not much beyond the measure of a full inspiration, it will pass into the blood only, and not into the cellular texture.[107]

The experiments of which I have given the detail, exemplify phenomena which do not indeed take place in the ordinary process of inspiration, and therefore I allow that no very rigorous induction can be drawn from them, with respect to the passage of deleterious substances into the mass of the blood; nevertheless it appears to me, that they very much confirm the probability of such fact, which besides is demonstrated by many of the preceding remarks. I shall conclude, then, that such passage is real. In fact, we have seen 1st, That the sole transmission of the black blood into the arteries, will not account for the infinitely various phenomena exemplified in the different sorts of asphyxiæ; 2dly, That the simple contact of the deleterious substance with the nerves of the lungs, can by no means be the cause of a death so rapid as that which is occasioned by these accidents; 3dly, That, therefore, we are forced as it were to suspect the passage of the poison itself into the blood; 4thly, That a number of considerations are in favour of such suspicion, and thus that the fact is proved both directly and indirectly.[109]

This principle being once established, a variety of results must flow from it. Of the first of these, of the mode of action, namely, which the deleterious substance must exercise upon the different organs, I shall say nothing, having nothing to offer but conjecture.

I shall accordingly content myself with inquiring what system it is which is particularly influenced by these substances, when mingled with the blood.—Now, 1st, This system appears to be the nervous one, and that portion of it especially, which presides over the parts of the animal life, the organic functions being only secondarily affected; 2dly, Of all the nervous system, the brain is that part which is the most affected; 3dly, Under this relation Monsieur Pinel appears to me to have been right, in placing some of the asphyxiæ (those for instance which are occasioned by the presence of a deleterious substance) among the neuroses. On this head the following considerations should leave us little doubt.

1st, In all the asphyxiæ, when the presence of a deleterious substance cannot be doubted, the symptoms consist of two general and opposite sets of phenomena, of spasm and torpor. Of two workmen who had come up out of the sewer of the street St. André des Ares, the one sat himself down upon a bulk, and fell into a state of asphyxia; the other with irregular convulsive movements, proceeded as far as the rue Battoir, and then fell down asphyxiated. The Sieur Verville, in consequence of inhaling the breath of a man who was lying in a state of asphyxia from the vapour of lead, fell down suddenly, and in a short time became convulsed. The vapour of charcoal intoxicates, as it is said. I have seen animals asphyxiated with other gases, and perishing with a stiffness, such as could be produced only by the most violent spasm. The centre of all these symptoms, and the organ from which they emanate, undoubtedly is the brain, and they depend upon its irritation or compression.

2dly, The animal life is always interrupted before the organic life, wherever the asphyxiating cause has been of a compound nature. Now the centre of the animal life is the brain.

3dly, I have proved when the animal perishes from the circulation of the black blood in the arteries, that the brain is especially affected even then; but in the same way, that is, by the cephalic arteries, the deleterious substance itself, may be introduced into the brain.

4thly, I have pushed a variety of deleterious gases (for example, sulphurated hydrogen) into the brain, and also some of those substances which vitiate the nature of these gases. The animal has always perished with symptoms of spasm, or torpor, and in general the death which is occasioned by the different gases, is always similar to that which is produced by the introduction of pernicious substances into the brain.

5thly, The consequences of these asphyxiæ, when life has been restored, invariably suppose a lesion of the cerebral system, such consequences consist of palsy, tremour, wandering pains, and derangements of the exterior apparatus of the senses.

From all these multiform experiments and considerations, we may surely conclude, that it is on the brain and nervous system that the deleterious principle, introduced into the blood, must act; from the death of these parts, that of the others is derived.

In this case the different organs no doubt are directly enfeebled, and may perhaps be immediately affected by those principles, which flow into them together with the blood, but all such phenomena, are even more visible in the animal, than in the organic life.

Let us not forget however, that a part at least of the cause of this sort of death, consists in the influence of the venous blood upon the organs, and that this influence must ever be in proportion to the length of time that such blood continues to circulate. The differences then which are found in the asphyxiæ, may be said to proceed from the greater or less effect of the venous blood upon the system, from the different nature of the various deleterious substances inspired, and from the age and temperament of the individual affected.

II. In the greater number of diseases, death commences in the lungs.

I have just spoken of sudden death. I shall now enlarge a little on that which is the slow effect of disease. Physicians must be well persuaded, that by far the greater number of diseases, put an end to life by an affection of the lungs. Whatever be the seat of the principal affection, be it either an organic lesion, or a general disorder of the system, the action of the lungs in the latter moments of existence, becomes embarrassed, the respiration difficult, and the oxydation of the blood, but slowly effected; accordingly this fluid must pass into the arteries, almost in the venous state.

The organs therefore which are already enfeebled, must be much more readily affected by the pernicious influence of such blood, than those which are subject to it, in the different cases of asphyxia. In this way the loss of sensation, and intellect, are very shortly the effect of embarrassment in the lungs; and ensue as soon as the brain begins to be penetrated with the fluid which is so transmitted to it.

By degrees the heart and all the organs of the internal life, cease also to move. It is here the black blood which arrests these vital motions, which have already been enfeebled by the disease. Such weakness, the consequences of the disease, is very rarely the immediate cause of death, it only prepares it, by rendering the organs more susceptible of the alteration in the healthy state of the blood. Such alteration is almost always the immediate cause of death. The disease then, is only an indirect cause of death in general, it kills the lungs, and the death of the lungs occasions that of all the other parts.

From hence it may be easily conceived, why the small quantity of blood contained in the arterial system of the subject, is almost always black. For 1st, The greater number of deaths begin by the lungs. 2dly, We shall see that those which have their commencement in the brain, are equally the cause of this phenomenon. Accordingly there can be only those, in which the heart ceases suddenly to act, after which the red blood can be found in the aortic ventricle, and auricle. Such appearance is seldom found, excepting in the bodies of persons who have perished from extensive hemorrhagy.

From the frequency of deaths beginning with an embarrassment of the lungs, may be conceived also the reason, why this organ is so frequently gorged with blood in the carcase in general, the longer the agony, the heavier and fuller are the lungs. When such fulness is found, together with black blood in the red-blooded system, whatever the disease may have been, it may be pronounced that death has begun in the lungs. In fact the concatenation of the phenomena of death is from one of the three organs, from the lungs, brain, or heart, to all the others. Now when death begins in the heart, the pulmonary vessels are generally empty, and there is red blood in the aortic system. On the other hand, if death has begun in the brain, there is then indeed a certain quantity of blood in the arteries, but the lungs are empty, unless, when gorged with blood, by some antecedent affection.