434 



CHAPTER II. 

 DISCOVERY OF THE CIRCULATION OF THE BLOOD. 



Sect. 1. Prelude to the Discovery. 



THE blood-vessels, the veins and arteries, are as 

 evident and peculiar in their appearance as the 

 muscles; but their function is by no means so 

 obvious. Hippocrates 1 did not discriminate veins 

 and arteries ; both are called by the same name 

 ; and the word from which artery comes 

 means, in his works, the windpipe. Aris- 

 totle, scanty as was his knowledge of the vessels 

 of the body, has yet the merit of having traced the 

 origin of all the veins to the heart. He expressly 

 contradicts those of his predecessors who had de- 

 rived the veins from the head 2 ; and refers to dis- 

 section for the proof. If the book On the Breath 

 be genuine (which is doubted), Aristotle was aware 

 of the distinction between veins and arteries. 

 " Every artery," it is there asserted, " is accom- 

 panied by a vein ; the former are filled only with 

 breath or air 3 ." But whether or no this passage 

 be Aristotle's, he held opinions equally erroneous ; 

 as, that the windpipe conveys air into the heart 1 . 

 Galen 5 was far from having views respecting the 



1 Sprengel, i. 383. 2 Hist. Animal, iii. 3. 



3 De Spiritu. v. 1078. 4 Spr. i. 501. 5 Ib. ii. 152. 



