52 DISEASES OF THE HORSE’S FOOT 
of cells gradually moving from off the surface of the finger 
or papilla like a cast), and similar casts are passing from off 
all the fingers or papille.’ 
From this description it will be noticed that each down- 
growing tube of horn bears a striking resemblance to the 
growth of a hair, described on p. 47. In fact, the horn tube 
may be regarded as what it really is, a modified hair. 
We next continue Professor Mettam’s illustration, and 
note how the modified hairs or horn tubes become as it 
were matted together to form the hoof wall. The cells 
lining the depressions are also proliferating, and their 
progeny serve to cement together the hollow casts of the 
papille, thus giving the inter-tubular substance. We have 
thus produced hollow tubes, united together by cells, all 
arising from the rete Malpighii of the coronary corium. 
Section of the lower part of the horn tubes shows them to 
contain a cellular débris. 
Thus, in all, in the horn of the wall we find a tubular, an 
intertubular, and intratubular substance. In fact, hairs 
matted together by intertubular material, and only differing 
from ordinary hairs in their development in that they arise, 
not from papille sunk in the corium, but from papille 
projecting from its surface. 
Although this disposes of the wall proper, there still 
confronts us the question of the development of the horny 
lamine. To accurately determine this point it is abso- 
lutely essential to examine, histologically, the feet from 
embryos. 
In the foot of any young ungulate in the early stages of 
intra-uterine life horizontal sections will show a covering 
of epidermis of varying thickness.* This may be only two 
or three cells thick, or may consist of several layers. 
Lowermost we find the cells of the rete Malpighii. As 
some criterion of the activity with which these are acting, it 
may be noted that with the ordinary stains their nuclei 
take the dye intensely. The cells of this layer rest upon a 
basement membrane separating the epidermis from the 
* Equine foetus, seventy-seven days old. 
soca 
