AN ANATOMICAL STUDY ON THE 



The matter is obvious in animal experimentation. 

 If an opening be cut not only in the aorta, but even 

 in a small artery, as Galen claims, in man, the whole 

 blood content may be drained from the entire body, 

 from veins as well as arteries, in almost half an 

 hour's time. 



Butchers can also well enough confirm this point. 

 In killing an ox by cutting the arteries of the neck, 

 the whole mass of blood may be drained off and 

 all the vessels emptied in less than a quarter of an 

 hour. We know how quickly an excessive hemor- 

 rhage may occur in removing a tumor or in an 

 amputation. 



The force of this argument would not be lost by 

 saying that blood flows equally if not more from 

 veins than from arteries, in butchering or amputa- 

 ting. The contrary of this really holds. Because they 

 collapse, and have no power to propel blood, and 

 because there is a block where the valves are placed, 

 as shall be shown later, the veins really pour out 

 little blood. The arteries, however, squirt it out in 

 quantities, with force, as if ejected from a syringe. 

 The matter may be tested by cutting the artery 

 in the neck of a sheep or dog, but leaving the vein 

 alone, and it will easily be seen with how much 

 force, in what amounts, and how quickly all the 

 blood in the body is drained, from veins as well 



and around. The introduction of quantitative evidence into phy- 

 siological problems was Harvey's great philosophical contribution, 

 and he apparently realized it, for he uses it again and again with 

 telling effect. 



I78] 



