VESALIUS. 81 



them as being analogous to the valves of the heart, but 

 he denies to them the office of valves. To him the 

 motion of the blood was of a to-and-fro kind, and valves 

 in the veins acting as such would have interfered with 

 anything of the sort. He expresses clearly the idea, that 

 was entertained in the old physiology, of the attractions 

 exerted by the various parts of the body for the blood ; 

 and especially that of the veins and heart for the blood 

 itself. " The right sinus of the heart," he says, " attracts 

 blood from the vena cava, and the left attracts air from 

 the lungs through the arteria venalis (pulmonary vein), 

 the blood itself being attracted by the veins in general, 

 the vital spirit by the arteries." Again, he speaks of the 

 blood filtering through the septum between the ventricles 

 as if through a sieve, although he knows perfectly well 

 from his dissection that the septum is quite impervious. 



It will thus be seen that the physiological teaching of 

 Galen was left undisturbed by Vesalius. 



