270 



MANUAL OF HISTOLOGY. 



individuals according to race, and in the same individual ac- 

 cording to the part of the body. The dark skin of some races 

 depends upon the presence of pigment in the cells of the rete 

 Malpighii. In the white race, dark pigment is usually pres- 

 ent in greatest quantity in the areolse of the nipples and in 

 the scrotum and labise. 



General structure. The skin is composed of the follow^ 

 ing parts : epidermis, corium, subcutaneous connective tissue, 



-.-.* 



e 



FIG. 114. Diagrammatic perpendicular section through the normal skin : a, epidermis ; b, rete Mal- 

 pighii; c, papillary layer; d, corium; e, panniculus adiposus; /, spirally bent end of excretory sweat- 

 dnct ; (7, straight portion of excretory duct of sweat-gland ; A, coil of sweat-duct ; ', hair-shaft ; *, root 

 of hair ; /, sebaceous gland. After Neumann. 



blood-vessels, nerves, lymphatics, sweat and sebaceous glands, 

 hairs, and nails. 



A perpendicular section through the skin shows (Fig. 114) 

 three well-marked layers ; the most superficial is called the 

 epidermis proper, a, b ; the middle layer is the corium or cutis, 

 d ; and the deepest layer the subcutaneous connective tissue, e. 

 The limit of the epidermis at its place of union with the corium 

 is sharply defined, but the corium and subcutaneous connec- 



