THE HISTORY OF THE SCIENCE OF ZOOLOGY 375 



but rather as a compiler of facts, amid some fables, the 

 former borrowed largely from Aristotle. After Pliny's 

 time the sciences declined and up to the sixteenth century, 

 with few exceptions, no contributions of note were made 

 to the science of zoology. 



Sixteenth century. — During the sixteenth century there 

 came a revival of the study of animals instituted chiefly 

 by the interest in the anatomy of the human body. During 

 this period, Conrad Gesner published (1551-1558) his 

 Historia Animalium, a work of forty-five hundred folio 

 pages, in which he recognized four groups of animals : 

 viviparous quadrupeds, oviparous quadrupeds, birds, aquatic 

 animals and serpents. Fabulous monsters were yet be- 

 lieved in, for he illustrated winged dragons, many-headed 

 hydrffi, and crowned basihsks. 



Seventeenth century. — In this century came a man whose 

 name will be inseparably linked with zoology for all time. 

 This was William Harvey who, in 1616, discovered and 

 demonstrated the circulation of blood. The discovery of 

 this truth must be accorded one of the greatest scientific 

 events of all time. Moreover, Harvey studied the embryol- 

 ogy and development of the chick and his contributions to 

 this phase of zoology are exceedingly important. Again, 

 in his famous phrase "omne vivum ex ovo," he enunciated 

 the principle that all living things arise from an ovum. 



During the period from 1590-1600 Hans and Zacharias 

 Janssen invented the compound microscope and, later, in 

 the seventeenth century, it was perfected so as to aid very 

 greatly in the study of animal structure and embryology. 

 Malpighi first studied the development of the chick with the 

 microscope, discovered and described certain organs of in- 

 sects — malpighian vessels — with which his name is still 



