322 MICROSCOPIC ANATOMY OF THE ORGANS. 



The horny cells are continually rubbed off from the surface 

 of the skin, and new cells are added from the basal layers of 

 the stratum Malpighii. In the lowest layers of the epithelium 

 we meet with karyokinetic figures. The young cells are pushed 

 out by still younger cells toward the surface. 



The skin of the white race is in various places colored 

 brown by the deposition of pigment (e. g., the skin of the 

 nipple, the labia majora, the scrotum, and around the anus). 

 Much coloring-matter is found in the skin of the negro. Here 

 very fine pigment granules are present between and in the epi- 

 thelial cells of the lowest layer of the stratum Malpighii, and 

 also in the outer parts of the corium in branched connective- 

 tissue pigment cells. The origin of the pigment is not defi- 

 nitely known. Some authors claim that the epithelial cells 

 have no power of producing pigment, and that the pigment 

 granules are imported by connective-tissue cells. Other au- 

 thors, on the contrary, hold that the cells of the epidermis are 

 capable of producing pigment granules without the assistance 

 of the connective- tissue cells, since it is an undoubted fact that 

 the pigment of the retina is a product of epithelial cells. 



(&) Hairs. 



The hairs are thread-like structures formed from the epi- 

 dermis, which are distributed over the whole surface of the 

 body with the exception of the. palms of the hands, the soles 

 of the feet, the red borders of the lips, and the inner surface 

 of the prseputium. 



A part of the hair (hair root] is buried in the skin ; while a 

 part projects beyond the surface (hair shaft) (Fig. 240). The 

 lower part of the hair root is thickened to form a rounded, 

 knob-like structure, the hair bulb. Into this there is pushed 

 from below a small round mass of the corium, which is called 

 the hair papilla. In small, fine hairs, the root extends into 

 the corium, while the roots of large hairs reach as far as the 

 subcutaneous fat. 



A true hair consists of horny epithelium. The part which 

 is situated in the skin is surrounded by several layers of epi- 



