DISEASES OF HORSES 295 



The superficial layer of the dermis is formed into a series of 

 minute conical elevations, or papilla, projecting into the deep por- 

 tion of the cuticle, from which they are separated by a very fine 

 transparent membrane. This papillary layer is very richly sup- 

 plied with capillary blood vessels and nerves, and is at once the seat 

 of acute sensation and the point from which the nutrient liquid is 

 supplied to the cells of the cuticle above. It is also at this point that 

 the active changes of inflammation are especially concentrated; it 

 is the immediately superposed cell layers that become morbidly in- 

 creased in the earlier stages of inflammation; it is on the surface 

 of the papillary layer that the liquid is thrown out which raises 

 the cuticle in the form of a blister, and it is at this point mainly 

 that pus forms in the ordinary pustule. 



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 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 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 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 skin of these parts into puckers, 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 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 pa- 

 pilla 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 overlapping each other like slates on a 

 roof in a direction 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 secre- 

 tion 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 im- 

 mersed in that medium. Besides those connected with the hair 

 follicles there are numerous isolated sebaceous glands, opening di- 

 rectly on the surface of the skin, producing a somewhat 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 



