640 ANATOMY AND PHYSIOLOGY OF THE HORSe’s FOOT. 
tion of epidermic or horn material thrown out from the 
“ keratogenous” membrane became converted or formified 
into cells, the same as those represented as constituting the 
mass of the hoof. 
Understanding the direction in which the fibres of this 
envelope pass or grow, it may therefore be received as an 
axiom, that the constant desquamation or wear taking place 
on the exterior of the horny covering in a healthy condition 
is compensated for by the cellular multiplication that is 
incessantly going on at the origin of the fibres from the 
surface of the living tissues, whereby these fibres, and conse- 
quently the entire hoof, are being continually pushed down- 
wards in mass by the deposition of new cells, the material for 
which is derived from the horn-producing membrane. 
This keratogenous membrane envelopes every part of the 
foot shielded by the horny carapace, and may be supposed to 
be allied to, or a mere continuation of, that covering the 
derm, and which constitutes the formative matrix of the 
cuticle. It, therefore, extends from the upper border of the 
perioplic ring, where the hair-roots cease to become im- 
planted, over the entire coronary and plantar cushions, the 
vascular laminae, and the sole. As, however, the hoof is 
composed of several parts which are somewhat dissimilar in 
structure and texture, it follows that the horn-generating 
membrane likewise differs in its function to a certain degree, 
and in points corresponding to these dissimilar portions ; but 
everywhere over its surface this membrane has the faculty of 
producing horn, though whether it usually does so or not in 
particular situations, and under ordinary circumstances, we 
will inquire hereafter. 
A proper understanding of the manner in which the hoof 
is formed, its mode of growth, and the various circumstances 
which influence these is of great moment to the farrier and 
scientific student, and must always be a subject of interest 
to those who are generally concerned with the welfare of the 
horse. For more than a century the structure, formation, 
and growth of this horny mass has been the subject of 
investigation and much dispute among men of science, no less 
than with some of those accomplished amateurs who have 
done so much to perpetuate a love for, and to increase the 
utility of, this indispensable creature; but it is only now 
that it can be said that the mystery which hung over very 
much pertaining to this subject is beginning to be solved 
through the enlightened and indefatigable exertions of a few 
eminent members of the veterinary profession. The import- 
ance and the great value to equine physiology and pathology 
