THE HORSE. 277 



Tertiary beds of central and western United States, Amer- 

 ica being tlie original home of the horse. The earliest 

 member of the series directly leading up to the horse was 

 Eohippiis, an older eocene form, about as large as a fox, 

 whicli had four well-developed toes and tlie rudiments of a 

 fifth on each fore-foot, and three toes beliind. In later 

 eocene beds appeared an animal {Oroliippus) of similar 

 size, but with only four toes in front and three behind. In 

 newer beds, i.e., lower miocene, are found the remains of 

 Mesohippus, which was as large as a sheep and had thi-ee 

 toes and the splint of another in each fore-foot, with but 

 three toes behind. In later miocene beds another form 

 {Anchitherium or Mi.ohippns) had the same number of 

 toes, but with the "splint bone of the outer or fifth digit 

 reduced to a sliort remnant." The splint Ijones, then, rep- 

 resent two of the digits of several-toed animals. Tlie suc- 

 ceeding forms were still more liorse-like. "In tlie Plio- 

 cene above, a three-toed horse (Hipparioii or Protoliippiis), 

 about as large as a donkey, was abundant, and still higher 

 up a near ally of the modern horse, with only a single toe 

 on each foot {PUohippu.s) makes his appearance. A true 

 Equus, as large as the existing horse, appears just above 

 this horizon, and the series is complete.'' (Marsh.) Fos- 

 sil horses extended over portions of North and South 

 America, but are supposed to have become extinct before 

 the present Indians appeared, thongli there are indications 

 that the horse was living on the plains of both North and 

 South America at the time of the discovery of the country, 

 and that the Indians used them. 



The horse {Equus caballus) is the most useful of all do- 

 mestic animals, and next to ships a prime means of the 

 diSusion of civilization. By artificial selection a great 

 number of varieties, races, and strains have been produced, 

 adapted for the performance of different kinds of work. 

 The horse only exists in a domesticated state. Sanson 

 states that the horse in the Orient has five, and in the west 

 (Africa) six lumbar vertebrae; in Arabia both forms occur; 



