i 74 PHYSIC 



dom for the external disposal of the effete and noxious 

 matter resulting from devitalisation and detachment. 



In the normal and healthy condition of the skin these 

 processes are accomplished with absolute perfection, the 

 cell proliferation and succession proceeding with vitally 

 determined precision ; so soon, however, as the age of the 

 individual or his environment, or both, leads to inter- 

 ference from within or from without with the regularity 

 of this process, so soon will appear the first indications 

 of the evolution of the phenomena of hyperkeratosis, it 

 may be only in the form of thickening and hardening of 

 the epidermis, with more or less consequent blunting of 

 the involved afferent nervature ; the condition, however 

 it may be, ultimately waxing in pronouncement until the 

 consistence of "sand paper" has been reached, or great 

 flakes and areas of accumulated epidermal debris mark the 

 affected parts. Such processes do or can only occur where 

 the skin is liable to be affected by changes in the environ- 

 ment of the body, as on the face and hands, or where the 

 development of pathological changes in the vitality and 

 texture of the skin elements have led to the occurrence 

 of stasis or arrest of cutaneous transpiration, perspiration, 

 or dermal cell proliferation and progression in one or all 

 of the dermal and epidermal strata. 



In the former or local the occurrence may hence be 

 seasonal or climatic, in accordance with the existence and 

 play of atmospheric change and condition, and the indi- 

 vidual susceptibility to such influences and pathogenic 

 incidence, while in the latter or general occurrence it may 

 be developed at any or all times, or whenever and wherever 

 the structural and functional conditions of the skin become 

 affected by an internal pathogenic influence, localised in 

 its power of action to a particular area, or spread over the 

 general surface of the peripheral covering and the cutaneous 

 excretionary machinery of the body. 



The substance, therefore, composing the hyperkeratosed 

 epidermis represents an exaggerated degree of the physio- 

 logically produced epidermal elements, and may be due 

 to defective shedding or aggravated production, which, 

 once initiated, may become the host of organisms dele- 

 terious to the health, and, it may be, fatal to the life of 



