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XVIII. Observations on the Development and Growth of the 

 Epidermis. By Erasmus Wilson, F.R.S., Lecturer on 

 Anatomy and Physiology in the Middlesex Hospital* . 



FT is the commonly received doctrine at the present day, that 

 the cells of the epidermis and of epithelium in general, 

 originate out of materials furnished by the liquor sanguinis or 

 plasma of the blood. In order that this purpose may be ef- 

 fected, the liquor sanguinis is conveyed by endosmosis through 

 the walls of the capillary vessels and through the peripheral 

 boundary of the surface, the " basement membrane " of Bow- 

 man. Having reached the exterior plane of the latter, the 

 changes commence which result in the development of gra- 

 nules in the previously fluid liquor sanguinis, or rather, 

 perhaps, in the aggregation of the molecules of the organi- 

 sable material or blastema, which was previously held in inti- 

 mate suspension or solution by the liquor sanguinis. Out of 

 the body an action of this kind would be termed coagulation, 

 and where inorganic matter is concerned, crystallization. The 

 process to which I am now referring, though taking place 

 within the body, is analogous to these phaenomena, with the 

 difference of being controlled and directed by the power of 

 life, of being, in point of fact, a vital coagulation or crystal- 

 lization. Indeed, coagulation, although occurring out of the 

 body, and sometimes after the lapse of a considerable period, 

 may be regarded as the last act of vital existence, or as a vestige 

 of the atmosphere of life with which the coagulating fluid was 

 previously charged in abundance. 



As regards the tissue under consideration, there is every 

 ground for belief, that the organisable material or blastema of 

 the liquor sanguinis is appropriated by the epidermis the very 

 instant it reaches the exterior plane of the " basement mem- 

 brane;" some portion of it, and the greater part of the serum 

 of the liquor sanguinis, being taken up by the newly-formed 

 cells to be transmitted in succession to more superficial ranges 

 of cells, and the remaining portion being converted on the 

 spot into the primitive granules of the tissue. This belief is 

 supported by the fact of the absence of any fluid stratum be- 

 tween the epidermis and the dermis, and by the close con- 

 nexion known to subsist between those two membranes. It 

 is well known that to separate the epidermis from the dermis, 

 until the former is so thoroughly saturated with fluid by ma- 

 ceration as to have acquired a considerable addition to its di- 

 mensions in all directions, or until decomposition has com- 



* Read before the Royal Society, June 19, 1845, and communicated by 

 the Author. 



