316 
ANATOMY OF THE HORSE. 
ordinary state of the hoof altogether imperceptible. For drawing 
our attention to this part we are indebted to Mr. Clark ; and 
insomuch as he considers it to be a production of the cutis (not 
having any connexion with the glandular circle that secretes the 
wall), and to serve the purpose of ie uniting the sensible parts 
with the insensible/’ we agree with him. We find something 
very similar to this growing upon the human nail, issuing from 
the superior edge of the terminating border of the cutis, and 
continued from the cuticle, which proceeds for some way upon 
the nail, uniting it more closely and firmly with the cutis, and 
protecting the latter from external injury. This production is no 
more the beginning of the nail itself than is the so-called frog- 
band the commencement of the wall : they are both distinct 
parts, though but supplementary ones, and seem to be of a 
nature partaking both of horn and cuticle. It has no more im¬ 
portant relation to the frog, in my opinion, than it has to the 
wall: it serves the same purpose to both,— that of strapping up the 
heels of the frog and binding them in closer and more intimate 
connexion with the neighbouring parts. Were I asked what other 
use it appeared to have, I should say, that it was formed to cover 
and protect from injury the new-formed horn of the hoof, guarding 
it in its passage downward, until it has acquired substance and 
hardness sufficient to resist external impressions of itself. 
Development of the Hoof. 
During the early months of fcetality, no horn or hoof is to be 
found. The foot is covered with a substance, white, firm, and 
elastic, resembling cartilage in its appearance, but proving more 
of the nature of cuticle on examination, which supplies the place 
of hoof. At the coronet this substance takes its origin from the 
cutis, being found to be continuous with the cuticle; but that 
which covers the bottom of the foot is a production from the sen¬ 
sitive sole and frog. Altogether, it possesses the general form 
and appearance of the hoof, differing however in these particu¬ 
lars—that the substitute for the wall is comparatively thin in 
its substance; while that which grows from the bottom of the 
foot is enormously thick, and, instead of being shaped into sole 
and frog, exuberates to a degree to constitute cub-footedness. 
About the same period at which the pastern and coffin bones 
take on ossification, horn makes its appearance underneath this 
cuticular wall, in the form of plates descending from the coronet, 
exhibiting with peculiar distinctness the lamellated structure. 
The horny wall becomes considerably advanced before we per¬ 
ceive any change in the bottom of the foot. At length, horn is 
detected forming underneath the cuticular substance, which, 
