MOTION OF THE HEART AND BLOOD 



pumped out. But as I have determined in the sheep, 

 the whole body does not contain more than four 

 pounds of blood. 



On this assumption of the passage of blood, made 

 as a basis for argument, and from the estimation 

 of the pulse rate, it is apparent that the entire 

 quantity of blood passes from the veins to the ar- 

 teries through the heart, and likewise through 

 the lungs. 



But suppose this would not occur in half an hour, 

 but rather in an hour, or even in a day, it is still 

 clear that more blood continually flows through 

 the heart than can be supplied by the digested food 

 or be held in the veins at any one time. 



It cannot be said that the heart in contracting 

 sometimes pumps and sometimes doesn't, or that it 

 propels a mere nothing or something imaginary. 

 This point has been settled previously, and besides, 

 it is contrary to common sense. If the ventricles 

 must be filled with blood in cardiac dilatation, some- 

 thing must always be pushed out in contraction, 

 and not a little amount either, since the passages 

 are not small nor the contractions few. This quantity 

 expelled is some proportion of the contents of the 

 ventricle, a third, a sixth, or an eighth, and an 

 equivalent amount of blood must fill it up in diastole, 



general use in Europe. This chapter is the crucial point in Harvey's 

 argument, and the first instance of the quantitive method in physi- 

 ology. It introduced the most important method of reasoning in the 

 science and demonstrated its most significant truth. 



[75I 



