OUTLINE OF THE STRUCTURE OF THE HORSE. 35 



The use of the membranes is to protect the organs which 

 they inclose. The serous membrane is very thin, yet hard 

 and tough. It is cut or penetrated with more difficulty than 

 any other part of the body, except the bones. From its 

 smooth surface, hurtful foreign substances readily glide oft*, 

 if the force with which they strike it be not very considerable. 

 One striking peculiarity of this membrane is its almost en- 

 tire insensibility. It is too thin itself to contain nerves or 

 blood-vessels of much size. A large number of these, how- 

 ever, lie immediately beneath it. It has no diseases, as yet 

 discovered, but may be torn or ruptured, of course. 



THE SKtN. 



The skin is the roof and covering of the horse's entire 

 structure. The hair forms an essential appendage of the 

 skin, and is most appropriately considered in connection 

 with it. This is the clothing of the horse's body, renewed 

 by ligature once a year. We extract from Youatt's excellent 

 work upon the English horse the following interesting de- 

 scription of the skin, and its functions : 



" The skin of the horse resembles in construction that of 

 other animals. It consists of three layers, materially differ- 

 ing in their structure and office. Externally is the cuticle — 

 the epidermis, or scarf-skin — composed of innumerable thin, 

 transparent scales, and extending over the whole animal. If 

 the scarf-skin is examined by means of a microscope, the 

 existence of scales, like those of a fish, is readily detected. 

 In the action of a blister, they are raised from the skin be- 

 neath in the form of pellucid bladders, and, in some dis- 

 eases, as in mange, they are thrown ofi^ in hard, dry, white 

 scales, numerous layers of which are placed one above 

 another. In every part of the body the scarf-skin is perme- 

 ated by innumerable pores, some of which permit the pas- 

 sage of the hair ; through others the perspirable matter finds 

 a passage ; others are perforated by tubes, through which va- 

 rious unctuous secretions make their escape; while through 

 a fourth variety numerous fluids and gases are inhaled. 



