OF THE SKIN. 135 



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 indistinctly laminated, a clear lamination is obvious in the 

 horny layer, inasmuch 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 con- 

 nected by their surfaces, and can only be detached and demon- 

 strated adhering together in numbers, by dissection, which is 

 much facilitated by boiling or macerating the epidermis. The 

 innermost, like the stratum Malpighii, taken altogether, 

 exhibit a wavy course wherever papillae exist, projecting out- 

 wards over the points of the papilke and following the depres- 

 sions between them. This takes place in the most striking 

 manner where very much developed papillae coexist with a mo- 

 derately 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 pa- 

 pillae 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 ex- 

 ternally 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 ex- 

 ternally the points beneath which the papilla?, are seated. In 

 the separate lamella? the plates are sometimes irregular, some- 

 times arranged circularlv, 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. 



