EXTRACT XXXI. 



ON HYPERKERATOSIS OF THE SKIN (Continued). 



KERATOSIS being a physiological process of growth and 

 devitalisation, and the last of the series undergone by the 

 solid or organised textures of the skin, it must naturally 

 follow that unless every step of that process follows the 

 normal course or direction an interruption or stasis will 

 be the result, or an altogether perverted course will be 

 initiated and continued, it may be, to a pathological 

 termination or hyperkeratosis. In other words, the shed- 

 ding of the skin is the final stage of the katabolic activity 

 of the natural vital growth or disposition of that portion 

 of the organised plasma and resultant egesta which reach 

 the periphery of the body, and necessarily, therefore, a 

 vital hygienic function of the very greatest moment to 

 the health of the body, and an occurrence, any interference 

 with which must lead to pathogenesis, in proportion to 

 the extent with which it interferes with the continuance 

 of the physiological work of life and health. 



Keratosis consists in the devitalisation, shrinkage, and 

 detachment of epidermal cells as they become proliferated 

 from the cutis vera and enter the stratum of overlying and 

 protecting epidermis, and that proliferation is rendered 

 possible only, or largely, by the presence in the proliferat- 

 ing dermic materials of a proper amount and proportion 

 of solid and liquid or plastic elements in order to the 

 maintenance of the succession of the cell outgrowth and 

 the double function subserved by the skin of affording a 

 containing and protecting wall to the body which it 

 encloses, while allowing at the same time organised free- 



