460 DISEASES or THE HOUSE. 



The fibrous bundles of the true skin contain plain, muscular fibers, 

 which are not controlled by the will, but contract under the influence 

 of cold and under certain nervous influences, as in some skin dis- 

 eases and in the chill of a fever, and lead to contraction, tightening, 

 or corrugation of the skin, contributing to produce the " hidebound " 

 of the horseman. Other minute, muscular filaments are extended 

 from the surface of the dermis to the hair follicle on the side to which 

 the hair is inclined, and under the same stimulating influences pro- 

 duce that erection of the hair which is familiarly known as " staring 

 coat." Besides these, the horse's skin is furnished with an expansion 

 of red, voluntary muscle, firmly attached to the fibrous bundles, and 

 by which the animal can not only dislodge insects and other irritants, 

 but even shake off the harness. This fleshy envelope covers the sides 

 of the trunk and the lower portions of the neck and head, the parts 

 unprotected by the mane and tail, and serves to throw the slrin of 

 these ^ifats into puckers, or ridges, in certain imtating skin diseases. 



The hairs are cuticular products growing from an enlarged papilla 

 lodged in the depth of a follicle or sac, hollowed out in the skin and 

 extending to its deepest layers. The hair follicle is lined by cells of 

 epidermis, which at the bottom are reflected on the papilla and be- 

 come the root of the hair. The hair itself is formed of the same kind 

 of cells firmly adherent to one another by a tough, intercellular sub- 

 stance, and overlapping each other, like slates on a roof, in a direc- 

 tion toward the free end. 



The sebaceous glands are branching tubes ending in follicles or 

 sacs and opening into the hair follicles, lined by a very vascular 

 fibrous network representing the dermis, and an internal layer of 

 cells representing the mucous layer of the cuticle. The oily secretion 

 gives gloss to the hair and prevents its becoming dry and brittle, and 

 keeps the skin soft and supple, protecting it at once against undue 

 exhalation of water and undue absorption when immersed in that 

 medium. Besides those connected with the hair follicles there are 

 numerous, isolated, sebaceous glands, opening directly on the sur- 

 face of the skin, producing a somewhat thicker and more odorous 

 secretion. They are found in large numbers in the folds of the skin, 

 where chafing would be liable if the surface were dry, as on the 

 sheath, scrotum, mammai y glands, and inner side of the thigh, around 

 the anus and vulva, in the hollow of the heel, beneath the fine horn 

 of the frog, on the inner side of the elbow, on the lips, nostrils, and 

 eyelids. When closed by dried secretion or otherwise these glands 

 may become distended so as to form various-sized swellings on the 

 sldn, and when inflamed they may throw out offensive, liquid dis- 

 charges, as in "grease," or produce red, tender, fungous growths 

 (" grapes.") 



