6 PRINCIPLES OF ANIMAL BIOLOGY 



Galen. — Rome, though succeeding to a dominant position in world 

 affairs, did not foster learning in scientific fields. Instead of an intellec- 

 tual revival during her period of prosperity, there was a notable decline. 

 Pliny lived in the midst of this decline. The last great biologist of 

 antiquity was Galen (131-210?), a physician living in Rome but of Greek 

 parentage. He dealt mostly with human anatomy and reveals a pro- 

 found admiration for the creator of so marvelous a mechanism. Every 

 organ had its use and was constructed on the plan best calculated to 

 serve that end. He was obliged to study these organs mostly in other 

 animals, for dissection of human bodies, once permirjsible, was in Galen's 

 time forbidden. When he describes the human hand, it is obvious that 

 the object before him is the hand of an ape. His errors are mostly 

 traceable to this necessity of using other animals. 



His accomplishments are numerous, such as his proof that the arteries 

 and the left side of the heart contain blood, instead of air as others sup- 

 posed, and his inference that the arteries and veins must be connected. 

 He seems not to have been fully appreciated in his own time, yet Galen's 

 books were for many centuries thereafter the standard of reference. 

 They were used in the medical schools, where anatomy was taught from 

 the desk with little or no demonstration, and modern criticism has given 

 to him a high measure of praise. 



The Dark Ages. — The thousand years and more following Galen's 

 time constitute the dark ages for biology as for other fields of learning. 

 Among the Arabs, who were dominant in the East, mathematics, astron- 

 omy, and chemistry made some advance, but writings in the field of 

 biology were mostly commentaries on the works of Aristotle and of Galen. 

 The division of the Roman Empire and the ravages of migratory peoples 

 in the West were not conducive to learning. Universities arose beginning 

 about the eleventh century, but these came to be controlled by religious 

 orders. The churchmen, finding a powerful ally in Aristotle's conception 

 of the earth as the center of the universe and his belief in a dominating 

 intelligence directing natural phenomena, turned the reverence in which 

 ancient philosophy was held to their own advantage. It took little guid- 

 ance from them to ensure that biological inquiry should consist merely 

 of commentaries on the writings of Aristotle, with no effort to ascertain 

 facts afresh. The views of the Greek natural philosopher were accepted 

 as correct even where simple observations could easily have proved them 

 wrong. The few books about animals which appeared in this era, aside 

 from the commentaries mentioned, contained only entertaining stories 

 and notes on the usefulness of animals to man. 



To deliver biology from the dominance of Aristotle, it was necessary 

 to destroy his system of thought. Aristotle, as was pointed out earlier, 

 based his theory of a universal order on an outside intelligence which 



