Page:Popular Science Monthly Volume 2.djvu/712

692 forth that outward activity which is peculiar to life; it droops, no intellectual manifestations occur, no impressions from light or sound are felt; but let a current of cool, fresh air touch the face, and life revives, the heart resumes it movements, color comes to the cheeks, and the phenomena of intellect and sensation reappear in the inverse order of their cessation. The English surgeon, Astley Cooper, produced similar phenomena in dogs by compressing the arteries of the brain at the neck; the animal fell into utter insensibility, and seemed to die. On suspending compression, cerebral life immediately returned; yet this was but an imperfect representation of what takes place in fainting. It was reserved for one of our own physiologists to go more deeply into the mechanism of the phenomenon. To bring life back again for a moment to a head severed from the body, and to restore it by the arterial blood, this was the problem which Brown-Séquard proposed and solved. The details of this memorable experiment were these: A dog is beheaded, and the head, still warm, separated from the trunk at the junction between the neck and chest. The evidences of life disappear by degrees, the eye losing its expression last. An electric current sent through the remaining part of the spinal cord no longer excites any contractions, the respiratory movements of the nostrils and lips cease entirely. After ten minutes have elapsed, Brown-Séquard adjusts to the four arteries of the head an arrangement of tubes communicating with blood deprived of its coagulable part, and charged with oxygen. By the help of artificial mechanism, imitating the action of the heart, the experimenter makes the blood circulate throughout the brain and spinal cord. A very few moments pass before irregular quiverings give life to the face, growing more decided, and at length movements reappear in all the muscles, and the eyes resume motion. "All these movements," says Brown-Séquard, "seem directed by the will." The experiment was continued for a quarter of an hour, and during all that time the vital manifestations and the appearance of their being voluntary continued. They soon ceased after the injection was stopped, and then followed the group of phenomena observed in dying, the pupil contracted and again dilated, and the last effort of life was a strong convulsion of all the facial muscles.

The naturalist experiences the strongest emotions at the sight of so extraordinary a spectacle. The physician now understands the necessity of contact between arterialized blood and the matter of the brain. He knows why a reclining position is proper in cases of fainting, giving easy access for the vivifying fluid to the brain. He knows that by throwing water on the face he will act upon the nervous centres, reanimate the movements of the heart, and cause circulation of blood in the mass of the brain. The philosopher asks himself one of those questions which are as old as the world, and more than ever of present interest, since the animated discussions of Barthez and Gabanis: Does or does not organized matter engender the phenomena