THE CIRCULATION OF THE BLOOD 441 



body ; and Galen, like his predecessors, imagined that the 

 " concocted " blood, having entered the great vena cava, 

 was distributed by its ramifications all over the body. So 

 that, in his view 

 (Fig. 2), the course 

 of the blood was 

 from the intestine to 

 the liver, and from 

 the liver into the 

 great vena cava, in- 

 cluding what we now 

 call the right auricle 

 of the heart, whence 

 it was distributed by 

 the branches of the 

 veins. But the whole 

 of the blood was not 

 thus disposed of. 

 Part of the blood, it 

 was supposed, went 

 through what we 

 now call the pul- 

 monary arteries (Fig. 

 1), and, branching 

 out there, gave exit 

 to certain " fuligi- 

 nous " products, and 

 at the same time 

 took in from the air 

 a something which 

 Galen calls the 

 pneuma. He does 

 not know anything 

 about what we call 

 oxygen ; but it is 

 astonishing how very 

 easy it would be to 

 turn his language 

 into the equivalent 

 of modern chemical 

 theory. The old 



philosopher had so just a suspicion of the real state of 

 affairs that you could make use of his language in many 

 cases, if you substituted the word " oxygen," which 



FIG. 2. The Course of the Blood according 

 to Galen (A.D. 170). 



