Marvels of the Universe 963 
working on this vast amount of material, Professor Osborn came to the conclusion that there is 
evidence of at least three (possibly four) collateral lines of development in the evolution of the horse, 
some large, some small, all more or less intermingled. His conclusions may be summed up briefly 
as follows : First, we have the little Eohippus (or “ Dawn Horse’), only eleven inches (or two and 
three-quarter hands) at the withers, 
with its wrist, or knee, near the ground. 
The hand was still short, with four 
little hoofs, and part of a fifth. It 
had a wide range in America and 
Europe. 
The next stage is seen in Hyra- 
cotherium, also known as_ Proto- 
rohippus. Its skull and fore-foot are 
shown in our illustration. It was a 
graceful little creature, about fourteen 
inches (three and a half hands) high at 
the withers. The next stage is seen 
in the Mesohippus. One finger has 
been dropped, and the skull is decidedly 
bigger, as our illustration will show. 
Here we see the middle, or third, digit 
getting larger. Unfortunately the skull 
of Protorohippus, which is the next 
stage, is unknown; but we have the 
feet, of which a fore-foot is shown in 
our illustration on the next page. 
Here the centre digit is much bigger, 
and this increase becomes still more 
striking in the Hipparion; until at 
last, in the modern horse, this one 
digit is supreme, and the others are 
only represented by the two feeble 
“ splint-bones ”’ already referred to. 
The outline restorations (2, 3, 4, 5, 
and 6 in our illustration on this page) 
may be studied in connection with 
the bones of the skeleton on page 
g62.. The Hipparion was of the size 
of a modern donkey. 
At the same time that these changes 
THE EVOLUTION OF THE HORSE. 
were taking place certain other im- 
Successive stages in the believed ancestry of the Horse. The first of 
portant changes, or adaptations, were 
the series (top) is the Dawn Horse, the second is the Hyracotherium, the 
going on in other parts of the body third Mesohippus; then come in order Protorohippus, Hipparion and the 
x ZA es modern Horse. 
(according to the Law of Correlation), 
especially in the number and structure, etc., of the teeth. These may be briefly summed up by 
saying that as horses grew bigger and swifter, their dental apparatus at the same time became 
improved, so that the food was more perfectly ground down, and thus more vital energy was 
provided. This fascinating subject is well illustrated by models and bones in the Natural History 
Museum, South Kensington. 
7O 
