6 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 histology. Toward the end of the seventeenth century 

 an effort was made to establish a scientific 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 depart- 

 ments. Such are the problems of race development or evolu- 

 tion, 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 physiology, and in 

 extending its scope to take in the lower organisms as well as 

 the higher and the single cell as well as the organs. 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: 



