435 



layer that tlie liquid is thrown out which raises tlie cuticle in the 

 form of a blister, and it is at tliis point mainly that pus forms in 

 the ordinary ])ustule. 



The fibrous bundles of the true skin contain plain muscular fil,ers 

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

 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 "starino- 

 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 Imirs 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, Avhich at the bottom are reflected on the papilla 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 direc- 

 tion towards the free end. 



The sehaceous glands are branching tubes ending in follicles or 

 sacks 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. Their oily secretion 

 gives gloss to the hair and prevents its becoming drv 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. Jk'sides those connected with the hair follicles there are 

 numerous isolated sebaceous glands, opening directly on the surface 

 of the skin, producing a somewhat thicker and more odorous secre- 

 tion. 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, scro- 

 tum, mammary glands and inner side of the thigh, around the anus 

 and vulva, m the liollow of the heel, beneath the fine horn of the fro- 

 on the inner side of the elbow, on the lips, nostrils, and evelids! 

 AV hen closed by dried secretion or otherwise these glands mav become 

 distended so as to form various sized swellings on the skin, and when 

 mfla ined they may throw out offensive liquid discharges as in " grease " 

 or produce red tender fungus growths ("grapes"). ' 



