THE LIMBS. 195 



lire, the "matrix of the hoof/' " subcorneous integu- 

 ment/' or " keratogenous membrane/' as it has been 

 called, may be divided into three portions, differing 

 in position and structure : 



1. A rounded, prominent ridge (" coronary cush- 

 ion"), convex from above downwards (Fig. 25, 12), 

 constitutes the upper edge of the hoof-matrix, im- 

 mediately contiguous to the hairy skin. It encircles 

 the front and side of the toe, descending on each side 

 behind and becoming continuous with the promi- 

 nences called respectively the glomes, branches, and 

 body of the frog. Its surface is everywhere covered 

 with numerous and well-developed little thread-like 

 prolongations, which, if it is placed in water, float 

 out, and give the surface a velvety appearance. These 

 papillae fit into corresponding tubular depressions in 

 the epidermic covering. From the coronary cushion 

 the base of the "wall" of the hoof (to be hereafter 

 described) grows; it therefore exactly corresponds 

 to that portion of the matrix of the human nail 

 which forms the bottom of the semilunar groove. 



2. Below this, and separated from it by a narrow 

 whitish band, the membrane has a very different ap- 

 pearance. It closely covers the front and sides of 

 the bone as far as its lower margin, and posteriorly 

 on each side is continued round the hinder border of 

 each of the lateral wings, and turns forward to reach 



