356 MORBID ANATOMY OF THE SKIN. 



must recollect notwltlistaiiding, that the continuity of the epithe- 

 lial layer is still quite unimpaired, and that there is no trace of 

 any exudation. Taking all these circumstances into account, we 

 can arrive at only one conclusion with regard to the essential 

 nature of the squamous exanthem, viz. that it is a morbid 

 growth taking place upon a decidedly inflamed base ; and that 

 this growth exhibits a ver}^ marked excess of, but — apart from 

 the imperfection of the cornifying process — no qualitative devia- 

 tion from, the normal course of cuticular development. The 

 squamous exanthem is an inflammatory overgrowth, and serves, 

 as such, to connect the foregoing sections with the ensuing one. 



/3 Hypertropln/. 



§ 300. AVhat has been said above (§ 83) with reference to 

 the physiological growth of epithelium and the extent to which 

 the subepithelial connective tissue takes part in the process, may 

 be transferred directly to the epidermis and papillary body. 

 The papillary body supplies the epidermis with young cells : 

 these are added to the rete Malpighii and gradually develope 

 into epidermic cells. A morbid over-activity of this process 

 forms the common basis of a great number of hypertrophic con- 

 ditions, which we are now about to consider. I say " a great 

 number," and I attribute the manifold variety of the appear- 

 ances presented, to the circumstance that the embryo-cell which 

 ultimately becomes an epithelial cell, is, before its emigration 

 from the connective tissue, one of its homologous constituents, 

 and is equally capable of contributing to the overgrowth of the 

 papillary body, when it is produced in abnormal quantities. The 

 very process which ultimately issues in the formation of epi- 

 thelial cells, if it be interrupted at an earlier stage, must inevit- 

 ably produce connective tissue. In including the overgrowth 

 of the epidermis and papillary body in one and the same chapter, 

 I have therefore been guided, not merely by the circumstance 

 that they are in fact nearly always associated in nature, but 

 also by the unity of the fundamental process which underlies 

 them both. The series opens with those forms in which the 

 epidermis alone is affected; it ends with those which are 

 limited to the papillary body ; the intermediate forms being 



