OF THE SKIN. 143 



greater than in the inner. Upon the body of the penis the cells mea- 

 sure 0-008-0-012 of a line; upon the glans, the largest are 0-016-0-02 

 of a line ; upon the outer side of the labia minora 0-012-0-02; on the 

 labia major a 0-010-016 of a line. These last, larger cells, all possess 

 distinct nuclei, and are almost identical with the epithelial plates, e. g. 

 of the cavity of the mouth and of the vagina (Fig. 56, 4). 



Whilst the stratum Malpighii, except in its upper layer, is but indis- 

 tinctly laminated, a clear lamination is obvious in the horny layer, inas- 

 much as its plates applied together horizontally, form strata in number 

 proportionate to the thickness of the horny layer (Fig. 55). It must 

 not be imagined that these strata are distinctly defined from one another ; 

 they are connected by their surfaces, and can only be detached and de- 

 monstrated adhering together in numbers, by dissection, which is much 

 facilitated by boiling or macerating the epidermis. The innermost, like 

 the stratum Malpighii, taken together, exhibit a wavy course wher- 

 ever papillae exist, projecting outwards over the points of the papillae, 

 and following the depressions between them. This takes place in the 

 most striking manner where very much developed papillae coexist with 

 a moderately thick rete Malpighii, especially in the palm and in the sole 

 of the foot, in which (see the figure in the section on the sudoriparous 

 glands), the horny layer penetrates so deeply between the papillae, that 

 its deepest cells are on a level with half their height : where the papillae 

 are smaller, the horny layer sinks less deeply between them, or even lies 

 quite flat upon the stratum Malpighii, as is the case where the papillae 

 are absent. From this cause the boundary-line between the horny layer 

 and the stratum mucosum in perpendicular sections, is sometimes straight, 

 sometimes wavy, with smaller or greater elevations and depressions. 

 The other parts of the horny layer take a more even course the further 

 they are from the mucous layer ; yet not merely in the hand and foot, 

 where, as is well known, the ridges of the corium are marked externally 

 upon the epidermis, but in many other localities, a slightly wavy course 

 of the uppermost layers may be perceived in perpendicular sections, and 

 slight elevations indicate externally the points beneath which the papillae 

 are seated. In the separate lamellae the plates are sometimes irregular, 

 sometimes arranged circularly, as around the excretory ducts of the 

 glands and hair-follicles, and also round the papillae on the palm of the 

 hand and sole of the foot, as may be seen most readily at the apertures 

 of the sudoriparous glands. 



43. As regards the color of the epidermis, in the white races, as 

 has been said, the horny layer is colorless and transparent or slightly 

 yellowish, the mucous layer yellowish white or brownish. The color is 

 deepest in the areola and in the nipple, passing even into blackish- 

 brown, especially in women during pregnancy and after they have borne 



