Page:Cellular pathology as based upon physiological and pathological histology.djvu/67

NAILS that to the innermost layer of the epidermis, very closely and almost abruptly, there succeed cells, which at first are also flattened, but in a less degree, and within which very distinct nuclei may be distinguished. These tolerabiy large cells mark the transition from the oldest layers of the rete Malpighii to the youngest of the epidermis. This is the point from which proceeds the regeneration of the epidermis, in itself an inert mass, which is gradually removed from the surface. And here is also generally the boundary, at which pathological processes set in. The farther we advance inwards, the smaller do the cells become; the last of them standing in the form of little cylinders upon the surface of the papillae (Fig. 16 r, r).

On the whole, the relations of the individual parts throughout the whole surface of the skin are everywhere the same, however manifold the peculiarities of detail may be, which the individual layers offer in respect to thickness, position, firmness, and connection. A section of a nail, for example, which in its external appearance certainly widely differs from ordinary epidermis, presents, nevertheless, on the whole, the same conformation, and has only one essentially distinctive feature, that, namely, in it two different epidermoidal structures are thrust, the one over the other, and thus a complication arises, which, if not duly attended to, may lead to the assumption of certain specific differences between it and other parts of the epidermis, whilst it really consists only in a peculiar change in the position of certain layers of

and near it little spindle-shaped, connective-tissue corpuscles, displaying at the base a reticulated arrangement, may be observed; to the left, a bulging out of the papillae, corresponding to a tactile corpuscle, no longer visible, and situated at a deeper level. R. R. The rete Malpighii; immediately around the papilla a very dense layer of small, cylindrical cells (r, r) ; more externally, polygonal cells, gradually increasing in size. E. Epidermis, consisting of flat and more closely packed layers of cells. S S. Duct of a sweat gland passing through. 300 diameters.