ZOOLOGY 



all that is to be known about them. In addition to displaying 

 our present knowledge of the relationship of animals, classifi- 

 cation serves a most important end in giving us more rapid 

 power of using that knowledge in getting further knowledge 

 that is needed. 



11. Historical. — Zoology as a science can scarcely be said 

 to be more than three hundred years old, although Aristotle, 

 more than three hundred years before Christ, wrote much of 

 value concerning animals. Later many facts of general anat- 

 omy were discovered in connection with the study of medicine, 

 and about 1600 the invention of the microscope opened up the 

 field of micro-organisms and of histology. Toward the end of 

 the seventeenth century an effort was made to establish a scien- 

 tific classification of animals. Since that time very much of 

 the attention of students of zoology has been turned in this 

 direction. During the last century however there has been a 

 constantly increasing interest in the study of embryology, of 

 histology, and in the general theoretical questions, the answers 

 to which depend on the bringing together of the results of 

 studies in all departments. Such are the problems of race de- 

 velopment or evolution, of heredity, of man's place in nature, 

 and the like. The most notable development of the subject in 

 recent years has been in connection with the study of the finer 

 structure of the cell, in more exact methods of studying physi- 

 ology, in extending its scope to take in the lower organisms as 

 well as the higher and the single cell as well as the organs, and 

 in inheritance. It is important to add that all this work is now 

 being done in a comparative way. The necessity of comparing 

 the histology, the embryology, and the physiology of one animal 

 with that of another arises from the belief in the unity of animal 

 life, and that all animals are really akin. If animals of different 

 kinds are really related, their likenesses and differences take on 

 a new meaning to the student, and classification comes to ex- 

 press the degree of kinship, as well as to serve the convenience 

 of the investigator. 



12. Summary. 



I. Natural Science embraces: 



