THE LIFE OF MAMMALS 
in the simultaneous appearance in the same ccuntries of the camel, which 
we positively know to have been an exclusively American-bred animal.” 
Whether or not enough remained to continue here the develop- 
ing race, at any rate America had many horses in Pleistocene or 
Preglacial times. In this era the northern hemisphere, af- 
fected by the advancing glacial cold, was continually becoming 
cooler and more rainy, yet the climate seems to have been, at 
least in the earlier part, highly favorable for horses, since a 
larger number of species, bigger than ever before, ranged over 
the plains and through the woods. One species about the size 
of a western bronco was numerous all over the South Atlantic 
states; a larger one inhabited the northwestern and middle 
states; while on the Pacific coast might have been seen a big 
one, the closest of all to the existing type. 
“Like the early cave horses of Europe, it had a large head, convex fore- 
head, stout limbs, spreading hoofs, and splint bones, which represent the 
last of the lateral toes.” Finally, there are found in Texas the skulls of a 
gigantic nag whose teeth indicate a bulk a third greater than that of a Bel- 
gian Percheron; while from Mexico has been obtained, on the other hand, 
the smallest species known. 
It is certain that South America was supplied with horses 
from the northern continent, and that there the stock, under 
the influence of novel conditions, gave rise to several species, 
some of which survived until after the advent of man, for their 
relics show that in Pleistocene times they were hunted and eaten 
by the savages of the period when glacial ice buried the major 
part of North America. This arctic condition in the North is 
reasonably supposed to have put an end to the horses, as well 
as many other animals then living here; but no such climatic 
disaster overwhelmed South America, where the favorable 
conditions remained unchanged, and where, when horses were 
reintroduced by the Spanish colonists, they ran wild, multiplied 
and flourished amazingly, especially on the pampas. No ade- 
quate explanation of their previous disappearance has been made. 
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