After Aristotle 69 



action the corresponding functions of the body, thus originated 

 as an expression of the primal force or pneuma. 



This physiology, we may emphasize, is not derived from an 

 investigation of human anatomy. In the human brain there 

 is no rete mirabile, though such an organ is found in the calf. 

 In the human liver there is no hepatic vein, though such an 

 organ is found in the dog. Dogs, calves, pigs, bears, and, 

 above all, Barbary apes were freely dissected by Galen and 

 were the creatures from which he derived his physiological 

 ideas. Many of Galen's anatomical and physiological errors 

 are due to his attributing to one creature the structures 

 found in another, a fact that only very gradually dawned on 

 the Renaissance anatomists. 



The whole knowledge possessed by the world in the depart- 

 ment of physiology from the third to the seventeenth century, 

 nearly all the biological conceptions till the thirteenth, and 

 most of the anatomy and much of the botany until the 

 sixteenth century, all the ideas of the physical structure of 

 living things throughout the Middle Ages, were contained in 

 a small number of these works of Galen. The biological works 

 of Aristotle and Theophrastus lingered precariously in a few 

 rare manuscripts in the monasteries of the East ; the total 

 output of hundreds of years of Alexandrian and Pergamenian 

 activities was utterly destroyed ; the Ionian biological works, 

 of which a sample has by a miracle survived, were forgotten ; 

 but these vast, windy, ill-arranged treatises of Galen lingered 

 on. Translated into Latin, Syriac, Arabic, and Hebrew, they 

 saturated the intellectual world of the Middle Ages. Com- 

 mented on by later Greek writers, who were themselves in 

 turn translated into the same list of languages, they were 

 yet again served up under the names of such Greek writers as 

 Oribasius, Paul of Aegina, or Alexander of Tralles. 



What is the secret of the vitality of these Galenic biological 

 conceptions? The answer can be given in four words. Galen 



