THE CIRCULATION OF THE BLOOD 443 



contracting and actively dilating. So that he is careful 

 to say that the nature of the pulse is comparable, not to the 

 movement of a bag, which we fill by blowing into it, and 

 which we empty by drawing the air out of it, but to 

 the action of a bellows, which is actively dilated and 

 actively compressed. ' 



After Galen's time came the collapse of the Roman Empire, 

 the extinction of physical knowledge, and the repression of 

 every kind of scientific inquiry, by its powerful and consistent 

 enemy, the Church ; and that state of things lasted until 

 the latter part of the Middle Ages saw the revival of learning. 

 That revival of learning, so far as anatomy and physiology 

 are concerned, is due 

 to the renewed influence 

 of the philosophers of 

 ancient Greece, and, in- 

 deed, of Galen. Arabic 

 commentators had 

 translated Galen, and 

 portions of his works 

 had got into the lan- 

 guage of the learned in 

 the Middle Ages, in 

 that way ; but, by the 

 study of the classical 

 languages, the original 

 text became accessible 

 to the men who were 

 then endeavouring to 



learn for themselves something about the facts of 

 nature. It was a century or more before these men, 

 finding themselves in the presence of a master finding 

 that all their lives were occupied in attempting to 

 ascertain for themselves that which was familiar to him 

 I say it took the best part of a hundred years before 

 they could fairly see that their business was not to follow 

 him, but to follow his example namely, to look into the 

 facts of nature for themselves, and to carry on, in his spirit, 

 the work he had begun. That was first done by Vesalius, 

 one of the greatest anatomists who ever lived ; but his work 

 does not specially bear upon the question we are now con- 

 cerned with. So far as regards the motions of the heart and 

 the course of the blood, the first man in the Middle Ages, 

 and indeed the only man who did anything which was of 



FIG. 3. The course of the blood from 

 the right to the left side of the heart 

 (Realdus Columbus, 1559). 



