DISEASES OF THE SKIN. 



Bj' M. R. Trumbower, D. V. S. 

 [Revised by John R, Mobler, V. M. D.] 



GENERAL DISCUSSION. 



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

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

 corium. 



The epidermis, cuticle, or scarf skin, is an 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 sensitive, contain- 

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

 dermis and attached to the underlying parts 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 layers, 

 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 papillae, 

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

 tissue. The blood vessels form dense capillary plexuses in the 

 corium, terminating by loops in the papilhe. 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 areola?. The follicle is dilated at the bottom to correspond 

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