230 SKIN, HAIR, AND NAILS, BY ALFRED BIESIADECKI. 



parallel to the surface of the skin. Even with high magnifying 

 powers, but little farther insight into the structure of this 

 layer can be obtained. Such insight can only be gained by 

 isolating the apparent fibres, and it is then seen that they are 

 composed of a number of flat polygonal scales, the so-called 

 epidermal scales, or horny laminae. 



In the deepest tier, lying in contact with the mucous layer, 

 the cells are rather thicker than those more superficially 

 placed, and resemble the uppermost cells of the mucous layer, 

 but are somewhat flatter than these, less granular, and do 

 not become stained with carmine. In most cases the nuclei 

 have entirely disappeared, but occasionally a flattened slightly 

 oval nucleus is visible, having an average diameter of 0*005 

 to O'OOS of a millimeter. The scales of the upper tiers are 

 flatter, of various form, crumpled, with a sharply defined 

 simple outline, nucleated and transparent. In water they 

 swell up to some extent, become opaque, darker, and more 

 granular; in acetic acid or caustic potash they become vesi- 

 cular, with fine fibres or granules in their interior, or with a 

 folded structure in the centre resembling a nucleus. The lami- 

 nation of the epidermis, that gives it the appearance of a 

 fibrous structure on section, arises from the firm adhesion to 

 one another of the scales of each tier. The stratum Malpighii 

 does not completely fill up all the inequalities of the surface 

 of the corium, but presents minute elevations at the points 

 corresponding to the projections, or papillse, of the latter; and 

 between these elevations are slight depressions. The lamel- 

 lated epidermis follows these elevations and depressions of the 

 mucous layer, which explains the wavy course of each lamella 

 on section. The whole epidermis, however, follows the deeper 

 furrows of the corium, as, for example, the ribs and furrows 

 of the palm, forming the well-known markings of the cuta- 

 neous surface. 



The thickness of the epidermis varies considerably in differ- 

 ent individuals and in different parts of the body. It often 

 forms a very thin membrane lying on a thick mucous layer, 

 whilst in many cases it is twice or three times as thick as the 

 latter. In both regions, however, the mucous layer maintains 

 a uniform thickness, with the exception only of those parts of 



