6 ANATOMY AND PHYSIOLOGY OP THE HORSE^S FOOT. 
more or less oblique to tlie cushion in the different regions of 
the foot, and in certain defects or maladies of the organ. So 
that it may be admitted, in principle, that the thickness of 
the wall increases in proportion as the cushion is in a position 
to secrete the horny fibres perpendicularly to its surface ; and 
that the wall has for its limit of thickness the projection of 
the coronet, which is parallel to the laminae. So far from its 
being the case that the thickness of this part of the hoof is 
equal to the width of the cushion, but depends on its projection, 
it may be remarked that in the young foal the cushion is very 
wide in front when compared with that of the adult, and yet 
the wall is very thin in this region. 
In addition to those above mentioned, we must not forget 
that other circumstances exist which may influence very 
materially the horn-producing function, and endow it with 
more or less activity. These influences, it appears, can be 
ranged in three categories, according as they may exert 
their action—1, on the entire organism, and indirectly on 
this function ; 2, in a manner less general and more direction 
the whole of the feet at the same time; 8, or on a single 
foot, and even on a circumscribed region of it. 
But, again, we have to remember that these influences do 
not operate to the same degree in every animal, for the simple 
reason that the secretory function does not possess the same 
activity in all; great variations being observable, not only in 
different breeds, but also between animals of the same race, 
according to individual dispositions and certain determinate 
conditions of structure, the recognition of which is important. 
In well-bred horses, in general, for example, the horn com¬ 
posing the hoof is denser, tougher, thicker, more polished on 
its surface, and finer in texture than in coarser bred animals; 
it is also better fitted to resist the effects of external agencies, 
and is regenerated with greater rapidity, as has been pointed 
out by M. Reynal. 
Among individuals, the variations in the rapidity with 
which the horn is generated are numerous and striking. 
There are some horses whose hoofs grow so slowly that from 
one shoeing to another there is scarcely enough horn formed 
to allow the new shoes a fresh bed, or the nails a hold in 
sound material; while there are others in which the produc¬ 
tion of this material is so active that in less than a month 
the hoofs have far exceeded their normal length, and require 
to be deprived of their excess by the tools of the farrier. 
Though it is not always easy to indicate the external signs 
which would lead one to prognosticate with certainty that 
the hoofs of one horse would grow rapidly and soundly, and 
