HOW THE OUTER SKIN FALLS OFF 155 



of fresh ones beneath them, and become 

 flattened by pressure ; they also become 

 gradually horny by evaporation and trans- 

 formation of their protoplasm into keratin, 

 till at last by rubbing they are detached at 

 the surface as dry, horny scales. There is 

 thus a constant production of fresh cells in 

 the deeper layers, and a constant throwing 

 off of the old ones from the free surface. 

 When these two processes are accurately 

 balanced the epidermis maintains its uniform 

 thickness. When by intermittent pressure a 

 more active cell-growth is stimulated, the pro- 

 duction of cells exceeds their waste, and the 

 epidermis increases in thickness, as we see in 

 the horny hands of the labourer. 



1 The Gutis vera. The corium, or cortis, 

 which rests upon a layer of adipose or cellular 

 tissue of varying thickness, is a dense and 

 tough, but yielding and highly elastic structure. 

 It is composed of nbro-cellular tissue, inter- 

 woven in all directions, and forming by their 

 interlacement numerous spaces or areolae. 



1 The Papilla, are conical elevations of the 



