Fifthly, If air be pushed into one of the divisions of the vena portæ from the side of the liver, it oscillates in the greater trunks of that organ for a considerable length of time, and arrives but slowly at the heart.—In this instance I have observed, that the animal experiences, only after a certain interval, those affections which are sudden when the fluid is injected into the veins of the principal system.[67]
Sixthly, The rapidity with which, in certain experiments, the annihilation of the cerebral action succeeds to the insufflation of air into the veins, might almost persuade us that such phenomenon is occasioned, as it is in wounds of the heart and syncope;—but 1st. The most simple inspection is sufficient to shew us that the heart continues to act after the apparent death of the animal.—2dly. As the motions of the heart are prodigiously accelerated by the contact of the foreign fluid, they push on the frothy blood with an extreme velocity, and hence we have the reason, why the brain in such case is so rapidly affected.
Seventhly, Were the cerebral action in this sort of death interrupted for want of movement from the heart, it would happen as it does in great hemorrhages of the aorta; that is to say, without violent convulsion. But here, on the contrary, the convulsion is extremely violent, immediately after the injection, and consequently, announces the presence of an irritating substance on the brain.
We shall conclude, that in the accidental mixture of air with the blood of the venous system, it is the brain which dies the first, and that the death of the heart is the consequence of the death of the brain. I shall explain in another place, in what way this phenomenon is occasioned.
FOOTNOTES:
[56] It is not true that a ligature on a nerve produces its effects only on the part to which this nerve is distributed; the brain is also affected; for, without this, how can be explained the pain that is felt, and the excitement, which is often sufficiently powerful to produce convulsions, and sometimes even death.
[57] The facts related here by Bichat are not conformable to those, which, the philosophers and physiologists have observed who have been more particularly engaged with this kind of experiments. Besides the consequences which he has drawn from them are not accurate, and he seems to be ignorant what course the galvanic fluid in this case takes.
[58] If there is always a relation between the vital energy of the brain and its alternate motions, it is because there is a constant relation between these motions and the entrance of the blood into the organ. Thus then, instead of considering this shock as the exciting cause of the brain is it not more natural to see in it only an effect purely accidental of the arrival of the arterial blood, which every thing proves to be the real excitant?
[59] As we know absolutely nothing of the manner in which the intellectual phenomena are produced in the brain, we cannot say whether compression prevents their development by stopping the motions with which the brain is habitually agitated, or by preventing the entrance of the arterial blood, or finally in some other way that we do not suspect.