662 ANATOMY AND PHYSIOLOGY OF THE HORSE'S FOOT. 
to their consideration than we have done to the parts just 
enumerated. 
Of these appendages, the first we will notice is the skin 
enveloping the lower part of the limb. 
Intimately associated with the foot, not only with regard 
to its position, sensitiveness, and vascularity, but also in 
relation to its secretory faculties, this membrane imme- 
diately above the hoof, and also its continuation within it, 
where it covers the exterior of the coffin bone, requires parti- 
cular notice, in order that we may the more fully and readily 
comprehend the large share allotted to it in the functions of 
the foot, and in the elaboration and integrity of its horny 
envelope — the hoof. Its structure, until it approaches the 
latter, is but little, if at all, different from that which it 
presents in other parts of the body. It is the same firm, 
resisting, more or less thin and elastic, hair-covered, and, as 
a rule, always dark-coloured membrane, that protects, while 
it permits the free movement of the important and sensitive 
organs beneath. It offers for study two layers, the derm 
(also named the cutis, or cutis vera), and the epiderm (like- 
wise designated the cuticle or scarf-skin). The first, as is 
well known, is the innermost, living, sentient, or fibrous por- 
tion of the skin, and forms the base of the epiderm. It is 
composed of a fibro-elastic tissue, the fibres interlacing more 
or less closely as they are superficial or deep-seated, and 
allowing the lodgment of blood-vessels, nerves, glands, fat, 
&c., in their meshes. The predominance of white or inelastic 
over the yellow or elastic fibres, depends upon the require- 
ments of the structures covered by the skin. Where elasti- 
city is necessary, as in the vicinity of joints, the yellow elastic 
fibres are most numerous ; but where fixity is needed, the 
white inelastic preponderate. When boiled, this layer is 
converted into gelatine, and tannin transforms it into the 
insoluble, compact, and supple material called leather; 
when exposed to maceration, it putrefies. Its surface is 
covered with what are called “ processes/' “ tufts," or “ pa- 
pillae," composed of blood-vessels and nerves; these are usually 
of a prominent conical or thread-like shape, and in greater or 
less profusion, according to circumstances. The glands are 
those minute bodies which secrete the perspiration, and 
also those which generally accompany, in pairs, each hair 
root, or follicle, and yield that sebaceous or oily matter 
destined to keep the integument flexible and in a healthy con- 
dition. The roots of the hair are also lodged in this layer, 
where it may be said they in reality grow ; lymphatic vessels 
are generally abundant. 
