INTRODUCTION 1 5 



messages to the muscles, by which the animal is en- 

 dowed with voluntary locomotion this is Physiology. 

 But horses are not the only living creatures in the world; 

 and if we compare the structures of various animals, as 

 the horse, zebra., dog, monkey, eagle, and codfish, we 

 shall find more or fewer resemblances and differences, 

 enough to enable us to classify them, and give to each 

 a description which will distinguish it from all others. 

 This is the work of Systematic Zoology. Moreover, the 

 horses now living are not the only kinds that have ever 

 lived; for the examination of the earth's crust the 

 great burial ground of past ages reveals the bones of 

 numerous horselike animals : the study of this preadam- 

 ite race belongs to Paleontology. The chronological 

 and geographical distribution of species is the depart- 

 ment of Distributive Zoology. Speculations about the 

 origin of the modern horse, whether by special creation, 

 or by development from some allied form now extinct, 

 are kept- aloof from demonstrative science, under the 

 head of Theoretical Zoology. 



2. History. The Greek philosopher Aristotle (384- 

 322 B.C.) is called the " Father of Zoology." Certainly, 

 he is its only great representative in ancient times, 

 though his frequent allusions to familiar works on anat- 

 omy show that something had been done before him. 

 His " History of Animals," in nine books, displays a 

 wonderful knowledge of external and internal structure, 

 habits, instincts, and uses. His descriptions are incom- 

 plete, but generally exact so far as they go. Alexander, 

 it is said, gave him nine hundred talents to collect mate- 

 rials, and put at his disposal several thousand men, for 

 hunting specimens and procuring information. 



The Romans accomplished little in natural science, 

 though their military expeditions furnished unrivaled 

 opportunities. Nearly three centuries and a half after 



