Physiological Researches on Life and Death

by Xavier Bichat

Without regard then to any system, let us inquire how the black blood, from its contact with the various parts, is the occasion of their death; how it acts on the parts of the animal life, and how it acts on those of the organic life.

All the organs of the animal life depend upon the brain; now, we have seen that the black blood paralyses the cerebral powers almost suddenly. In the state then of asphyxia, the locomotive, the vocal and sensitive organs, must be inactive. From the same cause, their exercise must be suspended in all those different experiments where black blood is injected into the brain, the other parts receiving the red blood as usual. But when the black blood circulates throughout all the system, when the whole of the organs, as well as the brain, are submitted to its influence, then there are two other causes of death connected with those which have been mentioned.

1st, The nerves, which are penetrated by it, for that very reason are no longer capable of keeping up the communication between the brain and the senses on the one hand, and on the other, between this same viscus and the locomotive or vocal organs.

2dly, The contact of the black blood with these organs themselves annihilates their actions. Inject the crural artery of an animal with the black blood taken from one of its veins, and the movements of that member will be shortly afterwards enfeebled, or wholly paralyzed. In this experiment, the upper part of the artery, for manifest reasons, should be that to which the pipe of the syringe should be fixed.

I am aware that as to this experiment, it may be asserted that the ligature of the artery, of itself, is capable of paralyzing the limb. In fact, such circumstance has happened twice with me, but I have also had occasion to observe, that it does not necessarily follow the ligature of this vessel, as it does the ligature of the aorta: when the latter vessel is tied, all movements cease at once; notwithstanding all which, the result of the injection of black blood, is almost constantly that which I have asserted it to be;—I say almost, 1st, Because I have once seen it fail in its effect, though done with the requisite precautions; 2dly, Because the debility, which is induced, both in duration and degree, will be according to the strength of the animal on which the experiment is made.

There is also occasioned in this experiment, a manifest suspension of the sensibility of the animal; it is not indeed so ready to appear as the loss of motion; but it always comes on, especially if the injection of the black blood be repeated three or four times, with small intervals.

A similar, but a more tardy effect may be produced by adapting to the canula, which has been placed in the crural artery of an animal, a tube which has been previously fixed to the carotid of another animal, and then by asphyxiating the latter.[96] The organs of the internal life are not dependent on the brain, and therefore are not affected by the suspension of the cerebral action in asphyxia. It is the influx of the black blood which is the immediate cause of their death.

I have already demonstrated what the influence is of this blood upon the organs of the circulation. We have seen how the heart ceases to act, as soon as it is penetrated by it; it is owing in part to the injection of the arterial and venous parietes themselves, by the vasa vasorum, that the vessels are forced to suspend their actions.

It will be always a difficult thing to prove, that the secretions, the exhalations, and the process of nutrition, could not be made from venous blood, because the circulation of this sort of blood in the arteries, does not continue for a sufficient time, to allow of observations, or the manner in which these functions would be affected by it. On this subject, however, I have made some essays. 1st, I exposed the inner surface of the bladder of a living animal, after having previously divided the symphysis pubis, and opened the lower belly, I then examined the oozing of the urine from the orifices of the ureters, while I asphyxiated the animal. 2dly, I divided the vas deferens, with the view of observing, whether the semen would flow or not, during such state.

In general, I have had occasion to remark, that during the circulation of the black blood in the arteries, no fluids appear to issue from the different secreting tubes. But I confess, that in all these experiments, and in other similar ones which I have made, the animal is too much agitated, and the limits of the experiments too circumscribed, for any thing like a well founded judgment to be formed on the subject in question. It is chiefly from analogy, then, that I am led to conclude, that the black blood is unfit for the purposes of exhalation and nutrition: such supposition also accords well with divers of the phenomena of asphyxia.—1st, The want of exhalation from the skin during the state of asphyxia, is probably the reason of the phenomena of the animal heat in such sort of death.[97] 2dly, In asphyxiating animals very slowly during digestion, I have uniformly observed, that the bile ducts, and duodenum, contain a much less quantity of bile, than they do at such time, when these parts are exposed in the living animal.—3dly, As the blood loses nothing from the exercise of these functions, it must of course accumulate in the vessels; and in fact, it is very fatiguing and unsatisfactory, to dissect the bodies of those who have been hanged or asphyxiated with the vapours of charcoal, from the fluidity and abundance of their blood. But this abundance, perhaps, may depend upon the weakness of the absorbents. In other sorts of death, the absorbents continue for some time to act upon the serous portion of the blood remaining in the vessels. In asphyxia there is neither secretion nor absorption.