8 ANATOMY AND PHYSIOLOGY OF THE HORSE'S FOOT. 
at successive depths or eras, commencing with the Palseo- 
therium and ascending to the Ilipparion — the fossil horse — 
each creation approaching, in the conformation of its foot, 
nearer to the Horse of our own geological epoch in solidity 
and simplicity. 
As has been observed by Professor Owen, the discovery of 
the remains of the Hipparion supplied one of the links, re- 
quired by Cuvier, between the Palseotherium and the Horse 
of the present day ; and it is still more significant of the fact 
of filiation of species, that the remains of such tliree-toed 
Horses are found only in deposits of that tertiary period which 
intervene between the older palseotherian one and the newer 
strata in which the modern Horse first appears to have lost 
its lateral hooflets. 
Through almost incalculable ages this tendency towards 
coalescence of the foot bones has been going on, and we see 
the result in the organ whose structure and functions we are 
now about to consider. 
It will be seen that the ultimate stage in the apparent 
unification of the pedal extremity is the formation of a most 
perfect piece of mechanism, in every respect corresponding to 
the other parts of the members, which have been justly desig- 
nated by the greatest of living anatomists, “ the best of ter- 
restrial locomotive organs.” In the perfecting of these 
limbs the whole mechanical force, it may be said, is concen- 
trated in a single hoof ; and we search in vain throughout 
the animal kingdom for a similar organ endowed with so 
many valuable qualities. 
True, the horse's foot has lost the prehensile faculty that 
so eminently distinguishes the hand of man and the quadru- 
manous animals — this has been transferred to the lips ; but 
it has gained others which are of far more importance, and 
which entitle it to be looked upon as the highest develop- 
ment of a locomotory organ. Nature appears to have ex- 
celled herself in the construction of a marvellous work, "which 
is at once a chef- d’ oeuvre of ingenuity, solidity, and simplicity, 
and in which complexity of function has been attained by 
the simplest means. For, in constructing the foot of this 
noble creature, she sought to do more than merely protect 
the extremely delicate and exquisitely sensitive structures 
contained within the hoof from injurious contact with the 
ground. This redoubtable difficulty is a comparatively in- 
significant one, if we consider the other portions of the task 
she set herself. It was necessary that the terminal extremity 
of the limb of such a glorious creation as the horse should 
be an organ endowed with the acutest tactile impressionability 
