HISTORICAL ZOOLOGY 269 



lished with respect to the number of teeth in a horse's mouth. 

 In this instance not one of the writers seems to have thought of 

 examining an animal, but all were satisfied to quote the words of 

 men who had died centuries before. This intellectual stagnation 

 was primarily due to the fact that all learning was in the hands of 

 the Church, and nothing was considered important except matters 

 pertaining to religion. 



4. ENCYCLOPEDIC PERIOD 



Conrad Gesner (1516-1565 A.D.) may be mentioned as one 

 of the best examples of this active but uncritical period. He 

 wrote many works, and his natural history (Historia Animalium) 

 was the best work on zoology for a long time. The activities of 

 the naturalists of this period foreshadowed the awakening of 

 ideas which were to throw off the respect for authoritative writ- 

 ings that had hampered the scholars of the Middle Ages. 



5. MODERN PERIOD 



Before the intellectual awakening of the sixteenth century, 

 naturalists essayed to cover the entire field of zoological sciences. 

 The workers of the Modern Period, however, have confined them- 

 selves to more limited fields, and certain individuals are respon- 

 sible in large part for the development of the various subsciences 

 defined in Chapter I. On this account the subjects of systematic 

 zoology, comparative anatomy, histology, embryology, physiol- 

 ogy, and evolutionary zoology are considered separately in the 

 following pages. 



a. Systematic Zoology 



Before the time of John Ray (1629-1705) there had been no 

 very definite idea of a species as such. Ray originated the modern 

 idea of a species, and defined it as the offspring of similar parents. 

 He published several lists of careful descriptions of the species 



