MOTION OF THE HEART AND BLOOD 



Meanwhile I know and state to all that the blood 

 is transmitted sometimes in a larger amount, other 

 times in a smaller, and that the blood circulates 

 sometimes rapidly, sometimes slowly, according 

 to temperament, age, external or internal causes, 

 normal or abnormal factors, sleep, rest, food, ex- 

 ercise, mental condition, and such like. 



But suppose even the smallest amount of blood 

 be transmitted through the lungs and heart at a 

 single beat, a greater quantity would eventually be 

 pumped into the arteries and the body than could be 

 furnished by the food consumed,^ unless by constantly 

 making a circuit and returning. 



amount in arterial blood. The minute-volume absorbed divided by 

 the arterial concentration gives the volume flow per minute through 

 the lungs, which divided by the pulse-rate gives the "stroke-volume" 

 of the heart. See also the Lancet, 2: 1265 and 1317, Dec. 19 and 26, 

 1925. The problem may also be solved in a relatively simple mechani 

 cal way, by x-ray pictures of the heart at systole and diastole (W. J. 

 Meek and J. A. E. Eyster, Amer. J. Roentgenol., 7: 471, 1920; Amer. 

 J. Physiol., 62'- 400, 1923; P. Hodges and J. Eyster, Amer. J. Roent- 

 genol., 12: 252, 1924). The next paragraph is an astonishing asser- 

 tion to make, and we are left to wonder how much of our supposed 

 recent knowledge of the physiology and pathology of the circulation 

 Harvey anticipated. The question regarding ventricular emptying, 

 of fundamental importance in cardiac pathology, is implied in the 

 second paragraph back, where it is indicated that there may be 

 variations in the relative quantities expelled. 



' This was the crux of the argument to Harvey, since the Galenists 

 insisted that blood was formed in the liver ("natural spirits") from 

 the food consumed, and distributed by the veins to nourish the parts 

 of the body according to their needs. Hence the emphasis placed by 

 Harvey in proving, by most conservative estimates, that the heart 

 pumps in a relatively short time more blood than is needed for nutri- 

 tion or than food can supply, more in fact than the whole weight of 

 the man or animal. Obviously it must be the same blood going around 



[77] 



