SECT. 44.] 



EPIDERMIS. 



89 



contain large elements, such as coarse granules, or oil-drops, for 

 instance, but a finely granulated matter, in which the granules arc 

 more or less distinct ; and these granules, without exception, become 

 more scanty in the more external cells. The nucleus is small in 

 the smallest cells (o - ooi3'" to o - oo25") ; in the large, larger (o - oo3'" 

 to 0005"); spherical or lenticular in the round and flattened, 

 oblong in the elongated cells. In the larger cells it appears dis- 

 tinctly as a vesicle, often with a nucleolus, and lies in the centre 

 amidst the contents ; in the smaller, it is, to all appearance, more 

 granular or homogeneous, without a perceptible nucleolus, and so 

 situated, that it not unfrequently touches the cell-wall. 



The cells of the mucous layer become pale in dilute caustic 

 alkalies, swell, and soon dissolve (the deepest layers first) into a 

 \mucous mass. Acetic acid acts upon these cells much less power- 

 ^llly, and is especially suitable for their examination. 





44. The horny layer, stratum corneum, constitutes the external 

 seni' -transparent portion of the epidermis, which, in the white 

 races, is colourless, and consists almost Fi s- 40 - 



entirely of uniformly constructed cells 4 



converted into plates. The deepest still 

 very much resemble the most superficial 

 cells of the mucous layer ; but even in 

 the second or third layer, the widely 

 deviating epidermic or horny plates are 

 to be found. They are real plates of 

 middling thickness, which, in the lower 

 and middle portions of the horny layer, 

 possess a tolerably regular, polygonal 

 form, and smooth surfaces; in the 

 upper layers, on the other hand, their 

 outline becomes more irregular, and 

 they are variously curved and bent, 

 and, therefore, often appear wrinkled 

 and folded. These plates must be con- 

 sidered as completely flattened cells, 

 furnished with a very small quantity of 

 a viscid fluid, and not as homogeneous 

 lamella?, formed entirely of the same 

 substance, as might appear at first sight; 



for on the addition of various re-agents, particularly of acetic acid 

 or caustic potass and soda, they swell and acquire the form of 



f l 



Horny plates of man. 1. Without ad- 

 dition, viewed from the surface; 2 and 3. 

 treated with water, granular and dark ; 

 4. nucleated plates, such as occur on the 

 outer surface of the labia minora, and on 

 the glans penis. Magnified 350 diameters 



