STRUCTURE OF THE EPIDERMIS MUCOUS LAYER. 227 



EPIDERMIS. 



Vertical sections of the skin show that the corium is covered 

 externally by a layer of cells distinguished as epidermis in its 

 wider sense, and, according to Malpighi, capable of division into 

 two superimposed layers, an external, the proper epidermis, 

 and an internal, the mucous layer, stratum mucosum Rete vel 

 Mucus Malpighii. The latter is composed of epithelial cells, 

 that fill up nearly all the depressions of the surface of the 

 corium, and consequently exhibit on their inferior surface 

 eminences or pits corresponding to the elevations or depres- 

 sions of that surface ; the former, on the other hand, is com- 

 posed of epidermal scales, that, arranged in lamellae, give to 

 the section a lamellar or fibrillated appearance. 



Mucous LAYER. 



The first series of cells composing the mucous layer do not 

 exceed 0'006 of a millimeter in diameter, are provided with an 

 oval nucleus, and are usually columnar in form, with their long 

 axes directed perpendicularly to the surface of the corium. 

 They consist of a slightly granular refractile mass of proto- 

 plasm, destitute of cell membrane, surrounding, though in small 

 quantity only, the compact nucleus. In many instances, as, for 

 example, in newly born children, the limits of these cells so 

 completely disappear that the surface of the corium appears 

 to be covered by a homogeneous layer of protoplasm, with 

 regularly distributed nuclei (Henle). The series of cells im- 

 mediately superimposed upon this layer are cubical. These 

 are of larger size, possess a better-defined outline, and an oval 

 feebly granular nucleus, in which two micleoli are often visible. 

 Their surface usually exhibits flat ribs or teeth. The cells of 

 the next three rows successively increase in size, assume a 

 polygonal form, and contain one, or occasionally two or three, 

 round nuclei. They are homogeneous in structure, with a dis- 

 tinct membrane, which in most parts of the skin gives off small 

 hairlike processes or prickles which penetrate the immediately 

 adjoining cells. (Rib or prickle cells of Max Schultze). The 

 nearer we approach the surface of the mucous layer, the more 



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