434 



disorder in llio skin may point at once and specifically to a particular 

 fanlt in diet, to an injudicions use of cold water when the system is 

 heated, to a fault in drainage, ventilation or lighting of the stables, 

 to indigestion, to liver disease, to urinary disorder, etc. 



STRUCTURE OF THE SKIN. 



The skin consists primarily of two parts: (1), the superficial non- 

 vascular (without blood vessels) layer, the cuticle or epidermis; and 

 (2), the deep vascular (with blood vessels) layer, the corium, dermis 



""'Thl^^/Z/c/c' is made up of cells placed side by side and more or less 

 modified in shape by their mutual compression and "^y/^'^^'^^'T^'. 

 ration and drving. The superficial stratum consists of the cells dued 

 in the form of scales, which fall off continually and form dandruff 

 The deep stratum (the mucous layer) is formed of somewhat rounded 

 cells with large central nuclei, and in colored skin containing numer- 

 ous' pigment ^granules. These cells have prolongations or branches 

 bv which the^' communicate with each other and with the superficial 

 layer of cells hi the true skin beneath. Through these they receive 

 nutrient liquids for their growth and increase, and through these 

 limiids absorbed by the skin, may be passed on into the vessels of 

 the true skin beneath. The living matter in the cells exercises an 

 equally selective power on what they shall take up for their own 

 nourishment and on what they shall admit into the circulation fi^m 

 without. Thus, certain agents Uke iodine and belladonna are readily 

 admitted, whereas others, like arsenic, are excluded by the sound 

 unbroken epidermis. Between the deep and superficial layers of the 

 epidermis there is a thin translucent layer (septum ucidum , con- 

 sistino- of a double stratum of cells, and forming a medium of transi- 

 tion from the deep spheroidal to the superficial scaly cuticle. 



The true skin or dermis has a framework of interlacing bundles of 

 white and vellow fibers, large and coarse in the deeper layers, and 

 fine in the superficial where they approach the cuticle. Between the 

 fibrous bundles are left interspaces which, like the bundles, become 

 finer as they approach the surface, and inclose cells, vessels, nerves, 

 o-lands, gland ducts, hairs, and in the deeper layers fat. 

 " The superficial layer of the dermis is formed into a series of mmu e 

 conical elevations or papUla, projecting into the deep ^fl^fj^" 

 cuticle, from which they are separated by a very fine traispaient 

 membi^ne. This papHUwu layer is very richly supplied with capil- 

 lary blood vessels and nerves, and is at once the seat of acute sens^a- 

 tion and the point from which the nutrient liquid is supplied to the 

 cdls of the cuticle above. It is also at this point that the active 

 changes of inflammation are especially concentrated; it is the immedi- 

 atel/superposed cell layers (mucous), that become morbid y increased 

 in the early stages of inflammation; it is on the surface of the papilla.y 



