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COMPARATIVE ANATOMY 



STRUCTURE OF THE HUMAN SKIN 



The skin of man, together with its appendages, hair, nails, teeth, mem- 

 brane bones, and glands, is only about four per cent of the body weight. 

 Like that of other mammals, it consists of two tissues, an outer epidermis 

 and an inner connective tissue corium. 



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SWEAT gland''-' 



Fig. 125. — A cross section of the thickened skin of the sole. The stratum corneum is 

 especially thickened on the sole and on the palm of the hand. 



A cross section of the epidermis shows under the microscope a many- 

 layered epithelium, which varies greatly in thickness in different parts of 

 the body. Even where it is thinnest, as for example on the back, at least 

 two layers of cells are distinguishable, an inner, growing stratum germina- 

 tivum and an outer, horny stratum comeum. The cells of the stratum 

 germinativum are columnar in shape; those of the stratum comeum are 

 flattened and scale-like. The former are alive, and by their constant 

 proliferation on division planes parallel to the surface of the skin, they 

 make continual additions to the strattun comeimi. The living cells in 



