THE l^ERIOPLIC RING. 67 



traced as far as the cleDches, where it commences to break down, 

 and is removed as flakes.* 



The corium consists of interlacing bundles of wliite fibrous 

 tissue, with a varying quantity of elastic fibres. Its surface is 

 papillated, i.e., it is broken up by innumerable conical promi- 

 nences, which, though of small size in most situations, attain a 

 relatively enormous development in others, such as the coronary 

 band, sensitive sole, frog, etc. 



A. THE HORX-SECRETIXG STRUCTURES. 



In the foot, stripped of its horny covering, five great divisions 

 of the horn-secreting corium may be recognised. In front and 

 at the sides, the perioplic ring, coronary band, and sensitive 

 laminae ; below, the sensitive sole and the sensitive frog. To 

 prepare a specimen for study, the foot may be macerated in water 

 for a few days. In from four to eight days, according to the 

 prevailing temperature, the hoof can be detached from the 

 vascular structures it covers. To preserve its form the hoof, 

 when removed, may be filled with liquid plaster of paris : 

 otherwise it loses its characteristic form on drying. 



1. The Perioplic PtiNG. 

 (Figs. 40 and 41, h.) 



The perioplic ring forms a band about one-sixth to one-quarter 

 of an inch broad, lying between the hair-bearing skin and the 

 coronary band, and extending completely round the foot to the 

 bulbs of the heel. In front it is somewhat broader than at the 

 sides, but its greatest breadth is attained close to the bulbs, 

 over which it extends to blend imperceptibly with the frog. 

 The perioplic ring, though somewhat deeper seated than the 

 hair-bearing corium, cannot be sharply differentiated from it. 

 On careful examination under water, it will be noted, however, 

 that between the last hairs are little papilke belonging to the 

 perioplic ring. The division between the coronary band and 

 perioplic ring is indicated by a well-marked, sharply-defined 

 linear depression, the coronary groove {Kronenfalz of Moller). 



The outer surface of the perioplic ring bears numerous, 

 closely-arranged, fine papilhe, from one to two twenty- fourths of 



* I am indebted to Professor Mettam for kindly supplying the foregoing 

 passages (pp. 61-67) on the skin.— [Jno. A. AV. D.] 



