TSE tlORSE. 
277 
Tertiary beds of central and western United States, Amer- 
ica being the original home of the horse. The earliest 
member of the series directly leading up to the horse was 
EoJiippus, an older eocene form, about as large as a fox, 
which had four well-developed toes and the rudiments of a 
fifth on each fore-foot, and three toes behind. In later 
eocene beds appeared an animal {Oroltipptts) of similar 
size, but with only four toes in front and three behind. In 
newer beds, i.e., lower miocene, are found tlie remains of 
Mesoliippiis, which was as large ns a sheep and had three 
toes and the splint of another in each fore-foot, with but 
three toes behind. In Liter miocene beds another form 
{Anchitherium or Mioliippns) had the same number of 
toes, but with the '^splint bone of the outer or fifth digit 
reduced to a short remnant.'^ The splint bones, then, rep- 
resent two of the digits of several-toed animals. The suc- 
ceeding forms were still more horse-like. ^^In the Plio- 
cene above, a three-toed horse {Hipparion or Prof ohipptcs), 
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 {Pliohippiis) makes his appearance. A true 
Eqinis, as large as the existing horse, nppears just above 
this horizon, and the series is complete." (Marsh.) Fos- 
sil horses extended over portions of North and South 
Americn,, but are supposed to have become extinct before 
the present Indians appeared, though 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 {Eqiius caialhis) is the most useful of all do- 
mestic animals, and next to ships a prime means of the 
diffusion 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; 
