421 



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 diseases 

 and in the chill of a fever, and lead to contraction, tightening, or cor- 

 rugation of the skin, contributing to produce the " hidebound " of the 

 horseman. Other minute muscular filaments are extended from the sur- 

 face of the dermis to the hair follicle on the side to which the hair is in- 

 clined, and under the same stimulating influences produce 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 mus- 

 cle, firml.y attached to the fibrous bundles, and by which the animal 

 can not only dislodge insects and other irritants, but even shake oft" 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 skin of these i)arts into i)ackers or 

 ridges in certain irritating skin diseases. 



The hairs are cuticular products growing from an enlarged papilla 

 lodged in the depth of a follicle or sack, 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 ijapilla and become 

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

 firmly adherent to each other by a tough intercellular substance, and 

 ovrrlappiug each other like slates on a roof in a direction towards the 

 free end. 



The sebaceous glands are branching tubes ending in follicles or sacks 

 and opening into the hair follicles, lined by a very vascular fibrous net- 

 work representing the dermis, and an internal layer of cells represent- 

 ing the mucous layer of the cuticle. Their 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 uudue exhalation of water 

 and undue absorption when immersed in that medium. Beside those 

 connected with the hair follicles there are numerous isolated sebaceous 

 glands, opening directly on the surface of the skin, i)roducing a some- 

 what thicker and more odorous secretion. These are found in large 

 numbers in the folds of the skin, where chafing would be likely if the 

 surface were dry, as on the sheath, scrotum, mammary 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 other- 

 wise these glands may become distended so as to form various sized 

 swellings on the skin, and when inflamed they may throw out offensive 

 liquid discharges as in " grease," or ijroduce red tender fungus growths 

 ("grapes"). 



The stveat glands of the horse, like those of man, are composed of 

 simple tubes, which extend down through the cuticle and dermis in a 

 spiral manner, and are coiled into balls in the deeper layer of the true 



