Page:The Harveian oration, 1875 (IA b22314611).pdf/33

the evidence of the senses. He says: —If a live snake be laid open, the heart will be seen beating quietly and distinctly for more than an hour, propelling its contents, becoming pale during systole, of a deeper tint during diastole. Now seize the vein with a forceps, or pinch it between finger and thumb; and the part between the point of pressure and the heart immediately becomes empty, while the heart itself grows paler and smaller, beats more slowly, and at length seems about to die. But remove the impediment, and the heart resumes both colour and size. Now compress or tie the artery instead of the vein, and the part between the obstacle and the heart, and the heart itself become inordinately distended, take on a deep purple colour, and at length are oppressed, and even choked, with blood. But remove the obstacle, and all things at once resume their pristine state—the heart regains its colour, size, and stroke. All this “may be observed more clearly than the noon day sun;” and we have before us illustrations “of two kinds of death; extinction from deficiency, and suffocation from excess.” The last of these forms of death Harvey recognised several times within two hours of death,