[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. [60] The organization of these animals differs too much from that of man to enable us to draw conclusions from one to the other, especially in what concerns the functions of the nervous system. There is an experiment of M. Dumeril in which a salamander lived a long time after the amputation of the head, till the formation of a perfect cicatrix in the neck, which intercepted the passage of air to the lungs. [61] Why are not the cerebral functions disturbed, when water is pushed slowly into the carotids? because there is then mixed with the blood of the artery too small a quantity of water at a time to enable this fluid to have a very evident action on the brain. But if this introduction of water into the mass of blood continues, whatever precaution may be taken, its effects soon show themselves. We have often, in our experiments, introduced a great quantity of water into the veins of an animal, and though much of it passed off by pulmonary transpiration, the arterial blood soon became very aqueous. Now, we have always observed, that in this case, the animals were struck with a kind of stupidity, which evidently indicated a want of action of the brain. [62] It is not uncommon to see patients, who retain their intellectual faculties perfectly, when the motions of the heart are so feeble, that they certainly cannot produce, in the mass of brain, any sensible jar.