Physiological Researches on Life and Death

by Xavier Bichat

FOOTNOTES:

[68] After the obliteration of the ductus arteriosus, the left ventricle receives no blood but what comes from the lungs; now, if the motions of the thorax continue, it is red blood; at least so long as the air is freely admitted into the bronchial tubes, and so long as the composition of this fluid is not changed by the mixture of foreign gases.

[69] These two modifications should, after what we have said, be reduced to a single one, viz. want of excitement of the brain by the arterial blood.

[CHAPTER IV.]
OF THE INFLUENCE OF THE DEATH OF THE HEART OVER THAT OF ALL THE ORGANS.

I shall divide this chapter, as the preceding one, into two sections. In the first I shall examine, how the death of the red-blooded heart, in the second how the death of the black-blooded heart, is the cause of the death of all the parts of the body.

I. On the death of the red-blooded heart, and how that of the organs is occasioned by it.

All the functions belong either to the animal, or to the organic life. Hence the difference of their classes. Now the death of those of the first class, in consequence of lesions of the red-blooded auricle and ventricle, is caused in two ways, and first, because the brain in such case is rendered inert from want of impulse, and can neither have sensations, nor exercise an influence over the locomotive and vocal organs.

Accordingly, all this order of functions is stopped, as when the encephalic mass has experienced a violent concussion. It is in this way that a wound of the heart, or the bursting of an aneurism, annihilate all our relations with external objects.

So strict a connexion between the movement of the heart, and the functions of the animal life, is not observable in those animals in which the brain, in order to act, does not require the habitual stroke of the blood. Tear away the heart of a reptile, or tie its large vessels, and it will continue for a long time to move and have sensations.

Besides, supposing even that the action of the brain were not to be suspended from lesions of the red-blooded heart, the animal life would not, on that account, be the less put an end to; because to the exercise of the functions of this life, is attached as a necessary cause, the excitement of its organs by the afflux of blood into them: now this excitement, both here and every where else, depends upon two causes.—1st, On the movement impressed, and 2dly, On the nature of the blood. At present I shall only examine the first mode of influence; the latter will come under our consideration, when we speak of the lungs.

Habitual motion is necessary to all the parts of the body alike, is a condition essential to the functions of the muscles, the glands, the vessels, and the membranes, &c. But this movement, which is partly derived from the heart, is very different from that which is communicated by the blood to the brain.

The latter organ receives an impulse by which the whole of its mass is visibly raised, an impulse, in the intermission of which the whole of its mass subsides. On the contrary, the interior movement, by which its particles are affected, is scarcely marked at all: and this depends upon the smallness and the delicacy of the vessels by which its substance is penetrated.

The contrary of this appearance is observed in the movement occasioned in the other organs by the influx of the blood into them: we see them neither rise nor subside; there is nothing like a general impulse made upon them, because, as I have said, such impulse is lost from the little resistance of the surrounding parts. On the contrary, they are penetrated by vessels of considerable magnitude, which create an intestine motion, oscillations, and impulses adapted to the actions of the tubes, lamellæ, or fibres, of which they are composed. This difference of movement may be easily conceived, by comparing the manner in which the brain on the one hand, and on the other the liver, the spleen, the muscles, or the kidneys receive their blood; indeed it is requisite that the brain should be distinguished from the other organs, in the manner of receiving its impulses, because it is enclosed in a case of bone, and consequently abstracted from the thousand other causes of agitation, to which the other parts of the body are exposed.

For we may remark, that all the other organs have about them a number of agents, which are destined to supply the place of that general impulse, which is wanting to them on the part of the heart. In the breast, the intercostals and diaphragm are continually rising and falling; the lungs and the heart are successively the seat of a dilatation and contraction. In the abdomen, there is an uninterrupted agitation produced, by the influence of respiration upon its muscular parietes; an incessantly variable state of the stomach, intestines and bladder. Lastly, from the various contractions of the muscles, the limbs have a still more evident cause of movement.

Nevertheless, it is probable that every one of the organs, as well as the brain, has a general though obscure movement impressed upon it, from the pulsation of the arteries; and hence, perhaps, we have the reason, why the greater number of the viscera, receive the impulse of the red blood upon their concave surfaces, as may be seen in the kidneys, the liver, the spleen, and the intestines. By such disposition, the impulse of the heart is less divided.[70]

From what has now been said, we may add another reason to that which we have before given, for establishing in what way the functions of the animal life are interrupted from cessation of action in the red-blooded heart. We may now also begin to explain the same phenomenon in the organic life. The reason of such interruption in both the lives is the same. It is as follows:

1st. In the case of death affecting the red-blooded heart; the intestine movement, which proceeds from the manner in which the arteries are distributed within the substance of all the organs, both of the one and the other life, is suspended; hence there exists no farther cause of excitement for the organs: they must consequently die.—2dly. The causes of the more extensive and general movements of the organs are abstracted; for almost all these causes depend upon the brain. We respire and move, only while the brain is alive: but as the brain must be in a state of collapsus, as soon as it ceases to receive the impulse of its blood, its influence must be evidently annihilated.

Hence it follows, that the heart exercises over the different organs two modes of influence; the one direct and immediate, the other indirect, and made through the medium of the brain, so that the death of the organs in consequence of the death of the heart, is immediate or mediate.

We have sometimes examples of partial death, analogous to this sort of general death. Thus, when the circulation is impeded in a limb, and the red blood no longer distributed to its parts, such parts become at first insensible and paralytic, then gangrenous. The operation of aneurism furnishes us with too many instances of this phenomenon, which by ligature, may be produced also in the living animal. Undoubtedly the principal cause of death in these cases, is the want of that stimulus which it is the business of the particles of the red blood to create, in contradistinction to those of the black blood, but the absence of the intestine movement in question, is by no means a less real cause of such death.

As for the interruption of the nutritive process, it cannot be admitted as a cause of the symptoms which succeed after the obliteration of a large artery. The slow, the gradual, and insensible way, in which this function is performed, does not accord with the sudden and instantaneous production of those symptoms, especially as they affect the animal life; for this is annihilated in the limb at the very instant when the blood ceases to flow into it, just in the same way as it is, when by the section of its nerves, the influence of the brain is abstracted.[71]

Besides the preceding causes, which, when the heart is dead, suspend in general the whole of the animal and organic functions; there is another cause of death which especially affects the greater number of the latter, such as the processes of nutrition, exhalation, secretion, and therefore digestion, which is only performed by means of the secreted fluid. This cause of death to which I refer, consists in the necessary stop which is put to these different functions, in consequence of their no longer receiving the materials upon which they are exercised. Nevertheless, such term arrives by degrees only, because they receive the materials on which they act, from the capillary, and not from the general circulation. Now the capillary circulation, is only subject to the influence of the insensible contractile powers of the parts in which it is performed; and is exercised independently of the heart, as may be seen in the greater number of reptiles, where the heart may be taken away, and the blood be notwithstanding observed to oscillate for a long time afterwards in the minuter vessels.[72] It is manifest, then, that whatever quantity of blood is left in the capillary system at the period of the death of the heart, will for some time afterwards be sufficient to keep up the functions in question, and that such functions in consequence will only gradually cease.

The following is a general view of the manner in which the annihilation of all the functions succeeds to the interruption of those of the heart.

The animal life is terminated—1st, Because the organs of which it is composed, are no longer excited without, by the movement of the neighbouring parts, nor within, by the blood.—2dly, Because the brain, from want of excitement, can no longer be a cause of excitement.

The organic life is terminated—1st, Because, as in the animal life, there is a want of external and internal excitement for its different viscera.—2dly, Because there is a want of the materials on which its functions are particularly exercised.

There are a number of other considerations, however, besides those which we have mentioned, which prove the reality of the excitement of the organs, from the movement communicated to them by the blood, as well as the reality of the cause, which we have asserted to be that of their death, when such excitement ceases.

For, 1st.—The organs which are penetrated only by the serum of the blood, such as the hair, the nails, the tendons, and cartilages, enjoy a less degree of vitality, and a less energetic action, than those in which the blood is made to circulate, either immediately by the heart, or by the insensible contractile powers of the parts themselves.

2dly.—When the white organs are inflamed, they receive an augmentation of life, a superabundance of sensibility, which frequently put them on a level in many respects with those organs, which in their natural state are endowed with the highest degrees of life and sensibility.

3dly.—Those organs which habitually receive the influx of the red blood, when inflamed, exhibit, in every instance, a local exaltation of the phenomena of life. In the two preceding instances, it is true, indeed, that the change of vital powers, precedes in point of time, the change which is made in the circulation; the organic sensibility of the part, has been augmented before the blood is carried thither in greater quantity; but afterwards it is the afflux of such increased quantity of blood, which keeps up the unnatural action which has been established. A determined quantity of blood in the ordinary state of the part, is necessary to the maintenance of that state; but when the part receives a double or triple increase of energy, its excitant also must be doubled or tripled; for in the exercise of the vital powers, there are always three things to be remarked; the power inherent in the organ; the excitant which is foreign to it; and the excitement which is the product of the two.

4thly.—It is doubtless, for this reason, that the organs to which the blood is habitually carried by the arteries, enjoy a degree of life, proportionate to the quantity of fluid by which they are injected. Such phenomenon may be observed in the glans penis, in the corpora cavernosa, in the nipple, in the skin of the face, and the actions of the brain, whenever the blood is directed with impetuosity towards them.

5thly.—The whole of the circulatory system, is thrown into greater action from the exaltation of the whole of the vital phenomena, just in the same way as the particular circulation of any part is augmented, when the particular phenomena of the life of that part are increased. The use of spirituous liquors, and spices to a certain quantity, is followed for a time by a general increase of energy in the powers of the system. The access of inflammatory fever will double and triple the intensity of life.

In these considerations I have only regarded the movement which is communicated to the organs by the blood. In another place I shall call the attention of the reader to that species of excitement, which is produced by the nature of the blood, by the contact of its component particles when in a state of oxydation or otherwise, with the different parts of the body. The reflections which I have offered, will be amply sufficient to convince us how much the blood, independently of the materials which it conveys with it, by its simple influx, is necessary to the activity of the organs, and consequently how much the cessation of the functions of the heart, must influence the death of the organs.