THE GROWTH AND SCOPE OF BIOLOGY 



monsters incapable of life; others, more fortunately constructed, survived 

 and gave rise to the animals of today. The blood he regarded as the seat 

 of intelligence, the eye he likened to a lamp, and respiration he thought to 

 occur partly through the skin. 



Democritus. — More important for natural science than any of his 

 predecessors was Democritus (Fig. 1) who was born about 460 B.C. 

 Chaste in morals and temperate in habits, he lived to the ripe age of a 

 century. Curious about the world, Democritus spent his patrimony in 

 travel, then lectured for pay to avoid the serious Greek charge that he had 

 wasted it. His interests were exceedingly inclusive, and he is best known 

 for a materialistic ("atomic") theory 

 of the universe, some features of which 

 have a distinctly modern flavor. 

 While it was through his general 

 philosophy that he most influenced 

 subsequent thought, not a few strictly 

 biological concepts are found in his 

 writings. He distinguished types of 

 animals differing in the quality of their 

 blood, a basis of classification later 

 adopted by Aristotle. In embryonic 

 development, he supposed the external 

 organs arose first, the internal struc- 

 tures later. He knew that mules are 

 sterile and conceived an anatomical 

 reason for it. He regarded the brain as 

 the organ of thought, the first of the natural philosophers to do 

 so. In his more subtle theoretical ideas, Democritus was strictly 

 materialistic; even the soul was regarded as a material thing, consisting 

 of globules of fire which impart movement to the body. He represents 

 the climax and close of the first scientific period of Greek philosophy, 

 which was an era of search for purely natural causes. 



Hippocrates. — A contemporary of Democritus was Hippocrates, 

 the Father of Medicine. What Hippocrates actually wrote is not cer- 

 tainly known. A collection of about a hundred works has been attributed 

 to him, but many of these were probably not his. His interest was 

 scarcely scientific, but rather in the healing of men; yet in one of the 

 works on diet in the collection is a reference to an attempt to classify 

 animals. While the study of medicine is biology, Hippocrates treated 

 it as an art; his descriptions of operations are models of clarity. The 

 social and moral responsibilities of physicians engaged his attention, 

 and a famous oath administered to medical graduates was based on his 

 teaching. 



Fig. 1. — Democritus. 



