DISEASES OF THE SKIN. 



liy M. R. Teumboweh, D. V. S. 

 [Hevised by John R. Mohler, V. M. D.] 



GENERAL DISCUSSION. 



The skin consists of two jjarts — a superficial layer, the epidermis, 

 or cuticle, and the deep, or true, skin, tlie dermis, cutis vera, or 

 corium. 



The epidermis, cuticle, or scarf skin, is ^n epithelial structure, 

 forming a protective covering to the corium. It varies in thickness, 

 is quite insensible and nonvascular, and consists of a sheet of cells. 



The epidermis is divided into a firm and transparent superficial 

 and a deep, soft layer. The latter is the rete mucosum, whose cells 

 contain the pigment which gives color to the skin. The deep sur- 

 face of the epidermis is accurately molded on the papillary layer of 

 the true skin, and, when removed by maceration, presents depres- 

 sions which correspond to the elevations on the dermis. From the 

 cuticle tubular prolongations pass into the sebaceous and sudorific 

 glands; thus the entire surface of the body is inclosed by the cuticle. 



The dermis, or true skin, is vascular and highly sensiti-^-e, contain- 

 ing the tactile ends of the nerves of touch. It is covered by epi- 

 dermis and attached to the underlying jDarts by a layer of areolar 

 tissue, which usually contains fat. The cutis consists of a fibro- 

 areolar tissue and vessels of supply. It is divided into two laj^ers, 

 the deep, or true, corium and the upper, or papillary. The corium 

 consists of strong interlacing fibrous bands, chiefly white ; its meshes 

 are larger and more open toward the attached surface, giving lodg- 

 ment to the sweat glands and fat. The papillary, or superficial, 

 layer is formed of a series of small conical eminences or papilla?, 

 which are highly sensitive, and consists of a homogenous, transparent 

 tissue. The blood vessels form dense capillary plexuses in the 

 corium, terminating ))y loops in the papilla?. The papillary nerves 

 run in a waving manner, usually terminating in loops. 



Hair is an appendage of the skin and forms its external covering. 

 It is a special modification of epidermis, having the same essential 

 structure, and consists of a root, shaft, and point. The root has a 

 bulbous extremity, is lighter and softer than the stem, and is lodged 

 in a recess or hair follicle, which may either be in the corium or sub- 

 cutaneous areolic. The follicle is dilated at the bottom to correspond 

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