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 papillse.' 



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 

 papillae, thus giving the inter-tuhnlsn- 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 debris. 



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 papillae sunk in the corium, but from papillae 

 projecting from its surface. 



Although this disposes of the wall proper, there still 

 confronts us the question of the development of the horny 

 laminae. 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. 



