STRUCTURE AND FUNCTIONS OF THE SKIN 



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THE STRUCTURE AND EXCRETORY FUNCTIONS OF THE SKIN. 



The skin serves, i, as an external integument for the protection of the 

 deeper tissues, and 2, as a sensitive organ in the exercise of touch, a subject 

 to be considered in the chapter on the Special Senses. It is also, 3, an im- 

 portant secretory and excretory organ; and 4, an absorbing organ. 5, It 

 plays an important part in the regulation of the temperature of the body by 

 controlling the loss of heat, i.e., a temperature-regulating function, discussed 

 in the chapter on Animal Heat. 



Structure. The skin consists principally of a vascular tissue named 

 the corium, derma, or cutis vera, and of an external covering of epithe- 

 lium termed the epidermis or cuticle. Within and beneath the corium are 

 embedded several organs with special functions, namely, sudoriferous glands, 



FIG. 304. Vertical Section of the Epidermis of the Prepuce, a, Stratum corneum, of very few 

 layers, the stratum lucidum and stratum granulosum not being distinctly represented; b, c, d, and 

 e, the layers of the stratum Malpighii, a certain number of the cells in layers, d, and e showing signs 

 of segmentation; layer c , consists chiefly of prickle or ridge and furrow cells; /, basement membrane; 

 g, cells in cutis vera. (Cadiat.) 



sebaceous glands, and hair follicles ; and on its surface are sensitive papilla. 

 The so-called appendages of the skin the hair and nails are modifications 

 of the epidermis. 



The epidermis is composed of several strata of cells of various shapes and 

 sizes; it closely resembles in its structure the epithelium of the mucous mem- 

 brane that lines the mouth or covers the cornea. The following four layers 

 may be distinguished; 



