FROM PARACELSUS TO HARVEY 



those given to-day first the contraction of the auricle, 

 sending blood into the ventricle ; then ventricular con- 

 traction, making the pulse, and sending the blood into 

 the arteries. He had thus demonstrated what had not 

 been generally accepted before, that the heart was an 

 organ for the propulsion of blood. To make such a 

 statement to-day seems not unlike the sober announce- 

 ment that the earth is round or that the sun does not 

 revolve about it. Before Harvey's time, however, it 

 was considered as an organ that was ' * in some mysteri- 

 ous way the source of vitality and warmth, as an ani- 

 mated crucible for the concoction of blood and the 

 generation of vital spirits." 3 



In watching the rapid and ceaseless contractions of 

 the heart, Harvey was impressed with the fact that, 

 even if a very small amount of blood was sent out 

 at each pulsation, an enormous quantity must pass 

 through the organ in a day, or even in an hour. Es- 

 timating the size of the cavities of the heart, and 

 noting that at least a drachm must be sent out with 

 each pulsation, it was evident that the two thousand 

 beats given by a very slow human heart in an hour 

 must send out some forty pounds of blood more than 

 twice the amount in the entire body. The question 

 was, what became of it all? For it should be re- 

 membered that the return of the blood by the veins 

 was unknown, and nothing like a " circulation " more 

 than vaguely conceived even by Harvey himself. 

 Once it could be shown that the veins were constantly 

 returning blood to the heart, the discovery that the 

 blood in some way passes from the arteries to the 

 veins was only a short step. Harvey, by resorting to 



