886 



THE SENSE ORGANS AND SKIN OF THE HORSE 



THE APPENDAGES OF THE SKIN 



The appendages of the skin are modifications of the epidermis, and comprise 

 the hairs, hoofs, claws, horns, etc. 



The hairs (Pih) cover almost the entire surface of the body in the domesticated 

 mammals, and some parts which appear at first sight to be bare are found on close 

 inspection to be provided with sparse and very fine hair. The hairs are constantly 

 being shed and replaced, but at certain periods in the horse, for example, they fall 

 out in great numbers, constituting the shedding of the coat. It is customary to 

 distinguish the ordinary hairs (the coat), which determine the color of the animal, 

 from the special varieties found in certain places. Among the latter are the long 



•■■ ' Ai^ '-^ \. . -^^ 



Fig. 709.- 



-Latbhal View of Horse to Show Hair-streams and Vortices. 



Kunstler.) 



(After Ellenberger-Baum, Anat. fiir 



tactile hairs about the lips, nostrils, and ej'es; the eyelashes or cilia; the tragi of 



the external ear; and the vibrissae of the nostrils. Other special features will be 

 noted in the discussion of the skin of the various species. The hairs are directed 

 in such a way as to form more or less definite hair-streams (Flumina pilorum), 

 and at certain points these converge to form vortices (Vortices pilorum) . 



The part of the hair above the surface of the skin is the shaft (Scapus pili), 

 while the root (Radix pili) is embedded in a depression termed the hair-follicle 

 (Folliculus pili). A vascular papilla (Papilla pili) projects up in the fundus of the 

 follicle and is capped bj^ the expanded end of the root, the bulb of the hair (Bulbus 

 pili). The hair-follicles extend obliquely into the corium to a varying depth; in 

 the case of the long tactile hairs they reach to the underlying muscle. Most of the 

 follicles have attached to them small unstriped muscles known as the arrectores 

 pilorum; these are attached at an acute angle to the under side of the deep part 



