ANATOMY AND PHYSIOLOGY OP THE HORSe’s FOOT. 641 
of some of the facts so acquired, must be the apology offered 
should this portion of the treatise become extended to a 
greater length than is consistent with the space at our dis- 
posal. 
With one exception, perhaps, it may be laid down as a rule 
that the horn found in contact with the living surface is 
formed from that surface. Pathological observation, no less 
than direct experiment, have proved the truth of this, and 
thus established the fact that distinct parts of the subongular 
membrane have a special function in the keratogenesis. 
Thus, the perioplic ring and fissure originate the periople. 
In proof of this, we see, when this horny band has been 
stripped off the living surface, along with a portion of the 
wall covering the coronary cushion, a semi-fluid horny 
matter thrown out from both surfaces, which meets at the 
bottom of the fissure and constitutes a regenerated periople 
and commencement of a new wall, the former overlapping 
the latter. 
Destroy the coronary cushion, hut leave the perioplic ring 
intact, though denuded of horn, and you have the periople 
again restored, but no wall; whereas if the ring be so 
seriously injured as to lose its function, but the cushion be 
merely deprived of its corneous growth, the former cannot be 
reproduced, though the latter is restored unaltered. 
Should the perioplic fissure alone be subjected to destruc- 
tion of its secretory power, as in a malady which is some- 
what unfrequent in well-conducted stables, while the perioplic 
ring and coronary cushion are merely laid bare, and the 
keratogenous membrane remains intact, the periople and 
wall grow down as usual from these surfaces, one above the 
other, but there is no adhesion or agglutination between 
them as when the fissure escapes without damage, and they 
remain isolated from each other. The continuation of the 
periople — the horny frog — is produced from the surface of 
the plantar cushion, which, externally, is identical with the 
perioplic ring. 
That the coronary cushion is the generator of the wall is a 
fact of which nearly every horseman is cognisant ; but that 
it is the source whence its entire mass, including the 
“ keraphyllae” or horny laminae is derived, has been much 
contested by veterinary authorities. That it is the matrix 
for the production of the fibrous portion of the wall is not 
disputed. As the wall is the most essential portion of the 
hoof, and as its reproduction in health and disease is a matter 
upon which the utility of the horse greatly depends, we can 
scarcely wonder that attention should have been most closely 
