544 iESTHESIOLOGY. 



The hair shaft consists of a centre or medulla, a surrounding 

 portion, and an external coating or cortex. The medulla consists 

 of cells containing pigmentary matter, is opaque, and usually 

 deeply coloured. All hair has not this medulla. The surround- 

 ing portion occupies the bulk of the shaft, and is composed of 

 elongated cells, which form horny fusiform fibres. The cortex is 

 merely a single layer of thin, flat, imbricated scales, which assume 

 a different appearance in the hair of animals of different species. 



About the muzzle of the horse are a number of largely-deve- 

 loped and strong hairs, commonly known as the cat-hairs, from 

 their resemblance to the whiskers of a cat. These are media of 

 touch, their bulbs receiving filaments of sensory nerves. 



Foot. 



In equine anatomy the word "foot" implies the hoof, together 

 with the bones and soft structures contained therein. Many of 

 these objects have already been described, so that our descrip- 

 tion here will be confined almost entirely to the hoof and the 

 internal structures with which it comes into immediate contact. 



In the broad sense we may regard the foot as consisting of 

 three well-marked portions — the basis or skeleton ; the highly- 

 sensitive secreting portion ; and the non-sensitive protective 

 portion. The two latter may be regarded as modifications of the 

 skin ; the sensitive part corresponding to the dermis or true skin, 

 while its covering, the hoof, corresponds to the epidermis, both 

 the latter structures being composed of a modified form of epi- 

 thelium, and each being secreted by the sensitive structures 

 within. 



The study of the foot of the horse is of the greatest practical 

 importance, owing to the many diseases and injuries to which it 

 is liable. It resolves itself here into the consideration of the 

 hoof or horny case, and the parts contained within it. 



The hoof of the horse corresponds to the nail of man, but it 

 is developed over the sides, and plantar aspect of the distal 

 phalanx, thus forming a protective horny case, enveloping 

 the inferior extremity of the digit. It is applied in an exact 

 manner to, and united most intimately with, the sensitive struc- 



