[63] A very considerable quantity of air can be forced into the veins of an animal, without causing its death, provided it be not pushed in suddenly. In all these cases, it is understood, that the quantity that can be thus introduced is in proportion to the size of the animal. I have before me at this moment the details of an experiment that I made on a horse at Alfort with M. Dupui, and in which, before the animal died, I was able, in thirty seven minutes, to inject quickly into the veins forty syringes full of air, and three syringes full into the carotid artery. (The capacity of the syringe was seventeen centilitres.) The animal died three minutes after the last injection. At the examination of the body, we found air in the azygos vein and in the thoracic duct, which contained much lymph, as well as the lymphatic vessels of the internal surface of the lungs. The heart was enormously distended with air mixed with a small quantity of blood. [64] This is not correct, and death takes place, on the contrary, by the cessation of the motions of the heart. The right ventricle is filled with air; and this air, dilated by heat, so distends it, that it can no longer contract. [65] The disorders which are produced in this case do not at all resemble those which follow the entrance of air into the veins. If we push towards the brain, by the carotid artery, a small quantity of air, we see almost immediately signs of a strong cerebral congestion, spasmodic stiffness of the muscles, loss of sensibility, and of the action of the senses, and all the phenomena of a real apoplexy. Respiration and the circulation go on some time without any apparent alteration, but finally these two functions become embarrassed and the animal sinks. Every thing leads to the belief, that the alteration in the circulation of the brain depends here on the presence of rarefied air in the ultimate arterial ramifications. When apoplexy is thus produced by the injection of air, if it be still forced into the artery, it breaks open violently a passage for itself, it tears the small vessels, and spreads in the parenchyma of the brain, which it makes emphysematous and crepitating under the finger. There finally returns a portion of it by the veins, which goes to the right cavities of the heart and which contributes to arrest the circulation. [66] In the two examinations related by Morgagni, it appears that after a sudden death, there was found in the vessels of the brain an aeriform fluid, to the presence of which, for the want of another material cause, was attributed the death of the individual; but there is no proof that this fluid might not be developed there after death. We shall now relate a more decided case of death occasioned by the presence of air in the blood vessels; but here there is no ground for doubt, because we know the circumstances of the introduction.