Page:The Harveian oration, 1875 (IA b22314611).pdf/31

than the whole body contains. Say that, in the sheep or dog, a single scruple of blood passes with each stroke of the heart; then, in one half-hour, about three-and-a-half pounds of blood would be injected into the aorta. This approaches the whole quantity which their bodies contain; for Harvey ascertained that in the sheep this does not amount to more than four pounds.

But if any one should object that the nutritive fluid derived from the food might quickly pass through the body in the guise of some abundant secretion, such as the milk, Harvey meets the objection by first naming the quantity of milk which an animal will yield in twenty-four hours, and then affirming that the heart by computation sends forth as much or more blood in an hour or two.

Passing over certain details relating to the quantity of blood in the body, and also to the causes which determine the frequency of the pulse, we come upon certain corroborative facts drawn from the phenomena of haemorrhage. Divide but a small artery, and the whole blood of the body will drain away in some half-hour or less; and the same thing occurs very rapidly in amputations,