THE SKIN. 



479 



Fig. 320. 



Finally, the thickness of the corium varies from ^' g to J- of an inch, 

 being J 5 to -fa of an inch in most places. It is thinnest (^ g to 5 V 

 of an inch) in the meatus auditorius externus, the eyelids, the red 

 border of the lip, and the glans penis and clitoridis ; and thickest 

 W* to T^ f an inch) on the back, chin, upper and lower lip, the 

 alee nasi, the ball of the sole, the extremity of the great toe, over 

 the scapula and the nates, and on the heel (even ^ to J of an 

 inch). 



2. The basement-membrane of the skin has been demonstrated 

 only in certain parts; and by Kolliker it is not recognized as one 

 of its histological elements in the adult ; though he admits it exists 

 in the embryo. It is merely a layer of 



simple membrane accurately covering 

 every part of the external surface of the 

 corium, and supporting the epithelium. 



3. The epithelium of the skin has al- 

 ready been in a general way described; 

 it being a compound scaly epithelium 

 (p. 240). Its outer layer, including the 

 harder portion removable by a blister, 

 is usually termed the epidermis, or cu- 

 ticle, or horny layer; and the remaining 

 internal portion, the stratum Halpighii, 

 or rete mucosum. The latter consists of 

 several layers of cells, the innermost 

 being 3^0 o to 2 o'ou f an mcn l n g> an( i 

 Wuu to 4t>W f an i ncn broad, and 

 placed perpendicularly to the surface of 



, c, , , Vertical section of the skin of the 



the corium. bometimes several layers thumb> 8howing the epidermis and 

 of perpendicularly arranged cells occur, outer la y er of the corium ; treated with 



. . _ . p acetic acid. a. Horny layer of the epi- 



glVing the deepest portion Of the Stratum dermis. 6. The Malpighian layer, 



Halpiahii a striated appearance. Upon Cori ' d ' Single papilla ' 



r 

 these, Several layers Of elongated Or 



round cells follow. (Figs. 146 and 320.) 



The cells in the outermost layer become h - Its passage through the homy 



1-1,1 , , i n, tion of the epidermis, i. Perspiratory 



flattened, and thus merge into those of pore . 



the cuticle or horny layer. The contents 



of these cells are never quite fluid, but are finely granulated, the 



granules invariably diminishing in the more external cells. In the 



negro these granules are colored, as has been shown by Fig. 68; 



c. 



e ' Com " 



pound papilla. /. Epithelium of the 

 perspiratory duct, continuous with the 



