Chapter XIII 



The Third Proposition is Proven^ and the 



Circulation of the Blood is Demonstrated 



from it 



SO FAR we have considered the amount of blood 

 flowing through the heart and lungs in the 

 body cavity, and similarly from the arteries to the 

 veins in the periphery. It remains for us to discuss 

 how blood from the extremities gets back to the 

 heart through the veins, and whether or not these 

 are the only vessels serving this purpose. This done 

 we may consider the three basic propositions proving 

 the circulation of the blood so well established, 

 so plain and obvious, as to force belief. 



This proposition will be perfectly clear from a 

 consideration of the valves found in the venous 

 cavities, from their functions, and from experiments 

 demonstrable with them. 



The celebrated anatomist, Hieronymus Fabricius 

 of Aquapendente, or, instead of him. Jacobus Syl- 

 vius, as Doctor Riolan wishes it, first described 

 membranous valves in the veins, of sigmoid or 

 semilunar shape,^ and being very delicate eminences 



* Hieronymus Fabricius of Aquapendente (1537-1619) was a 

 pupil of G. Fallopius (1523-1562) who was in turn the pupil of Ve- 

 salius (1514-1564). It was their establishment of modern anatomy 



[96I 



