320 ANATOMY AND PHYSIOLOGY OP THE HORSE’S FOOT. 
tion of cells. In other respects, nevertheless, there is the 
closest identity ; the cuticle also protects the parts within or 
beneath it, is composed of the same elementary tissues, has 
neither vessels or nerves, is destined to sustain external wear, 
and is a slow conductor of heat and cold. We even behold 
the epidermis, in various places exposed to external contact, 
assume different thicknesses, and consequently variations of 
density and resistance. The foot of the ostrich, for instance, 
is covered by an epidermis almost equal in thickness to the 
horse’s hoof, but it does not manifest the tubular arrangement 
of the hoof ; and so with the foot-pads of other animals. Even 
the human nail — w^hich is the analogue of the hoof — is 
nothing more than a collection of superposed cells, and 
remains a thick, hard, but unmodified epidermis showing no 
fibrous arrangement. 
The fibres of the hoof are constituted by concentric layers 
of compressed cells, named, from their identity with those of 
the cuticle, “ epithelial ;” these surround, and indeed form, 
the walls of every tubular fibre, and this arrangement is 
specially conferred upon this particular epidermic envelope in 
order to endow it with the exceptional strength and tenacity 
required in the performance of its extraordinary functions. 
Those who maintain that the hoof is only a collection of 
agglutinated hairs, offer what at first seems a plausible 
argument, in asserting that the hair bulb is simply transferred 
to the surface of the podal integument, and that instead of 
being imbedded for a part of its length in the substance of 
the epidermis, as in other parts of the body, the hair grows 
from its root on the face of the coronary cushion and else- 
where in the region of the foot ; and the bulbs being in 
contact, the hairs grow together and form the hoof; the 
periople, acting as a protection to these hairs while as yet 
they are immature, playing the part of a follicle. When, 
however, we examine more closely these so-called hairs and 
the parts from which they are supposed to grow, we find that 
they differ very materially from the capillary formation on 
other parts of the body. Hairs have not the simple irregular 
texture of the horn-tubes, but are complex bodies, com- 
paratively speaking, and offer but few points of resemblance 
to the hoof fibres. Besides, horses that are naturally entirely 
deficient of their pilous covering have hoofs as strong as those 
which are well clothed with hair; this would not be the 
case if the hair and horn were identical, as a deficiency over 
the body generally must affect the feet if there was any 
relationship between the tw r o. 
There is no more resemblance between the hoof and a bone 
