154 HUMAN SKIN 



moulded on them. This layer is of constant 

 uniform thickness in all parts of the skin. 

 The pigment of the skin, the varying quanti- 

 ties of which cause the various tints observed 

 in different individuals and different races, is 

 contained in the deeper cells of the Hete 

 mucosum. 



'It is a most remarkable fact that the 

 epidermis maintains its thickness in spite of 

 the constant wear and tear to which it is 

 subjected.' 



How the Outer SJcin is removed. 



The explanation of this is as follows : 

 1 The columnar cells of the Hete mucosum 

 elongate, and their nuclei divide into two ; 

 the upper part of each cell separates from 

 the lower ; thus from a long-columnal cell are 

 produced a polyhedral and a short columnar cell. 

 The latter elongates and the process is repeated. 



{ The polyhedral cells thus formed are pushed 

 up towards the free surface by the production 



* Kirkes, Handbook of Physiology. Morrant Baker's 

 Edition. (John Murray.) 



