642 ANATOMY AND PHYSIOLOGY OF THE HORSE^S FOOT. 
directed towards it. The controversy as to how its total 
mass, including the keraphyllse, is secreted, arises from the 
fact that its upper border, or cutigeral cavity, is in contact 
with the coronary cushion, while the whole of its inner fac^ 
is in juxtaposition to the vascular laminae. It is the exact 
share which each of these portions takes in the secretion of 
the wall that has given rise to discussion, and which has 
compelled me, at the commencement of this section, to make 
this division of the hoof a doubtful exception to the general 
rule laid down with regard to its formation. 
That the coronary cushion is the source from which the 
fibrous portion of the wall is generated, as already remarked, 
experiment and daily experience prove. When a piece of the 
wall is torn off at its origin as far as the white zone or lower 
margin of the cushion, so as to lay bare the living structures, 
but without seriously injuring the villi, in about a day a 
quantity of matter is thrown out which entirely covers these 
villi and the general surface ; in a fortnight or so this exuda- 
tion or elaboration of new horn has made such progress that, 
should the animal be destroyed, and its hoof removed by 
maceration, scarcely any difference can be perceived in the 
cutigeral cavity between the old material and that thrown 
out to repair the breach. Should the animal be allowed to 
live for a month instead of a fortnight, the newly formed 
horn constitutes a hard mass projecting even beyond the 
level of the other part of the wall, and has grown down more 
than a quarter of an inch during this period ; its inner aspect 
does not differ from the adjacent cutigeral space, and its 
texture is fibrous, though the fibres are markedly undula- 
ting. 
In three or four months this piece has grown something 
like an inch or an inch and a quarter from the termination of 
the skin, and though the exuberant growth at the commence- 
ment of its formation is still indicated by the prominent 
ridge of horn, yet the more recent growth has gradually 
subsided until that just thrown out is level and uniform with 
the undisturbed horn on each side, and the fibres have 
resumed their ordinary rectilinear direction. In eight or 
nine months the prominent ridge has reached the lower 
margin of the hoof, and the horn above it offers nothing 
dissimilar on either of its surfaces or in its texture to the 
other parts of the wall. 
This experiment, the effects of a blister, the actual cautery, 
and trifling or serious injuries to the coronet, all amply 
demonstrate that the surface of the coronary cushion is the 
chief, if not the sole agent in the production of the entire 
