CONTEXTS 



CHAPTER I. 



PAGE 



The Horse's Place in Nature — Its Ancestors and 



Relations 1 



Interest of the study of the horse, especially as illustrat- 

 ing some important principles in biology — A test case of 

 the value of the theory of transmutation of species — Sig- 

 nificance of rudimentary structures — Meaning of the term 

 "specialization" — Position of the horse in the animal king- 

 dom — Division of ungulate mammals into perissodactyle and 

 artiodactyle — The horse belongs to the former — Palasonto- 

 logical history of the perissodactyles — Generalized ungulates 

 of the earliest Eocene age — Phenacodus — True perissodac- 

 tyles — Hyracotherium — Palaeotherium — Families which be- 

 came extinct without leaving descendants — Three surviv- 

 ing families, represented at the present time by the Ta- 

 pirs, Rhinoceroses, and Horses— The first the least and the 

 last the most modified — Principal characters by which 

 horses differ from the generalized early forms of perissodac- 

 tyles, probably all adaptations to changed conditions of life 

 — Present state and probable future of the group. 



CHAPTER II. 



The Horse and its Nearest Existing Relations . . 45 



The tapirs (Family Tapiridce) — Characters, species, geo- 

 graphical and geological distribution— The rhinoceroses 

 (Family Rhinocerotidw)— The horses (Family Eqmdw)— 

 Their immediate predecessors — The hipparions, or three- 



