The morning call., 1892-06-12
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HOW EOhippus Grew.

rocks but in the anatomical structure OF the
horse himself. This differs very materially
from that of any other Of the mammals. 1t
is in the anatomical structure of the horses
leg tnat this difference is particularly
noticeable, and brief glance at this Will be
necessary 10 clear understanding OF our
subject To begin with, what is generally
called the knee of horse is in reality what
In the human anatomy constitutes the wrist.
The cannon bone corresponds to the middle
one Of the long bones (metacarpals) Of the
human hand The pastern, or ankle-bOne,
answers to the first phalaDx of the finger
the other two being represented By the
"corOnary" and ''cuffn' bones. Above the
knee is the real forearm, which in man and
the other QuadTupeds consists of two bones,
the uluar and radius. In the horse there
is apparently but one bone, the radius,
though examination reveals the exist
ence of rudimentaTy ulDa. an
chylosed with the larger bone, yet dis
tinctiy tTaeeable as separate In the very
Young fOal So n the hind extremity the
hock is really the heel, the bones below
that corresponding to the middle bones Of
the foot and the bones of the mddls toe.
The single bone Of the leg is in cOmbIna-
tiOn with what was evidently al one time
distinct and separate fbuia or smaller bone.
Now. on either side OF the cannon bone,
which is the bone between the so-called
knee" and ''ankle," appears in the horse
Of to-day " hat are called the "splint bones"
long, slender processes OF bone, terminating
in points and lying close TO the cannon
bone These are the remains OF the sec
0nd and fourth Of the five toes upon
which little eohippus scampered away from
his enemies in early eOcene. He had but
four toes on the front foot in the miOeene
age and three behind. he was called MO-
hippus then. and was as large as sheep.
The ulnar and fbular bones we're still
clearly defined, and 10 general appearances
he resembled very nearly the JaplT OF to-
day, from which we may infer that he was
not a handsome beast. Still increasing In
size the last of the miOcene, ana the dawnlng
Of the pliOcene time found him with but
three toes on his front foot and under the
name Of prOtOhippus or hippaTion. lie
was as large as the modern donkey, then
with a longer neck, a handsOmer head and
A more gracefully turned form than had
miohippus. The first and fifth toes had dis
appeared entirely, and his legs and teeth
had undergone important changes.
II IS in his teeth as we'll as IN his limbs
that the horse differs widely from the other
mammals. These are admirably adapted
for their work Of preparing rapidly and we'll
the food upon which the horse lives. Such
sharp, cutting teeth. such powerful and
wonderfully adapted grinders are not found
in any other animal. The latter are very
large and exceedingly complicated in strucl-
ure, being composed OF number OF sub
stances of varying degrees Of hardness, so
that the surfaces wearing away al different
rates are always uneven and IN good grind
ing condition. The twelve nclsors are
closely set IN the front part Of the mouth,
and, with their sharp, chisel-like edges, are
Powerful tools land can be used as danger
Gus weapons when occasion Tequires), the
wearing OF which forms up 10 the eighth
year a pretty good index Of the age
of the animal, and there is a large space be-
tween the last iucisor and the tyst molar on