History of Comparative Anatomy 335 



lution. Having become well acquainted with a large number of diverse 

 animal forms, invertebrate and vertebrate, he saw that it was possible 

 to arrange them in a graded series ranging from the smaller, simpler 

 invertebrates to larger and more complex animals such as mammals. 

 He proposed that the lowest living forms must have emerged somehow 

 from nonliving substance. The foot of his "ladder" (" scala naturae'") 

 rested on earth, and on the top rung stood man. He believed that the 

 higher forms of his "scala" were somehow derived from lower forms — 

 a genetic continuity of all living things. 



Of Aristotle's numerous writings, three great biologic works 

 have come down to us in more or less incomplete form — "Historia 

 Animalium," "De Partibus Animalium," and "De Generatione 

 Animalium." 



GALEN 



It was to have been expected that Aristotle's brilliant achievement 

 would have given to science, especially biology, an impetus which 

 would have carried it steadily forward through succeeding centuries. 

 But it did not. Following Aristotle's time comes a stretch of about 

 16 centuries during which science, as Aristotle conceived of it, showed 

 only occasional sparks of life. The brightest of these is seen in the 

 work of Galen (about 130-200 A.D.), a physician and anatomist of 

 Greek origin, born in Pergamum, Asia Minor. Much of his work was 

 done in Rome, where he was physician to the Emperor Marcus 

 Aurelius. His voluminous works are largely compilations of existing 

 knowledge and highly philosophic, but he made important contribu- 

 tions to human anatomy, his work on the muscular system being espe- 

 cially valuable. 



THE "DARK AGES" 



Immediately following Galen began a period of some eight centu- 

 ries, the "Dark Ages," during which science was at its lowest ebb. 

 During these earlier centuries of the Christian era, the prevailing theol- 

 ogy created an atmosphere unfavorable for science. Human interests 

 tended to shift from things of the present and of this world to a future 

 life in some other world. Human thought was dominated by authority. 

 It was enough that a physician of the time should know what Aristotle 

 and Galen had taught, but even the works of these authors seem to 

 have been largely forgotten. In medical schools, anatomy was taught 

 mainly from books and with very little dissection and demonstration. 



DAYBREAK — MEDIEVAL MEDICAL ANATOMY IN EUROPE 



Breaking of dawn after the long night occurred in the eleventh an' 

 twelfth centuries. The returning light entered Europe from the east 



