1136 



GENERAL ANATOMY OR HISTOLOGY. 



The epidermis or cuticle (scarf-skin) is non-vascular, and consists of stratified 

 epithelium (Fig. 678). It is accurately moulded on the papillary layer of the 

 derma. It forms a defensive covering to the surface of the true skin, and limits 

 the evaporation of watery vapor from its free surface. It varies in thickness in 

 different parts. In some situations, as in the palms of the hands and soles of the 

 feet, it is thick, hard, and horny in texture. This may be partly due to the fact 

 that these parts are exposed to intermittent pressure, but that this is not the only 

 cause is proved by the fact that the condition exists to a very considerable extent 

 at birth. The more superficial layer of cells, called the horny layer (stratum 

 corneum), may be separated by maceration from the deeper layers, which are called 



Epidermis 



or 

 Cuticle 



Derma 



Sweat-Glands 



Nutrient Artery 



FIG. 677. A sectional view of the skin (magnified). 



the rete mucosum or stratum Malpighii, and which consist of several layers of 

 differently shaped cells. .The free surface of the epidermis is marked by a net- 

 work of linear furrows of variable size, marking out the surface into a number of 

 spaces of polygonal or lozenge-shaped form. Some of these furrows are large, as 

 opposite the flexures of the joints, and correspond to the folds in the dermis 

 produced by their movements. In other situations, as upon the back of the hand, 

 they are exceedingly fine, and intersect one another at various angles; upon the 

 palmar surface of the hand and fingers and upon the sole of the foot these lines 

 are very distinct and are disposed in curves. They depend upon the large size 

 and peculiar arrangement of the papilla? upon which the epidermis is placed. The 

 deep surface of the epidermis is accurately moulded upon the papillary layer of 

 the dermis, each papilla being invested by its epidermic sheath ; so that when this 

 layer is removed by maceration, it presents on its under surface a number of pits 

 or depressions corresponding to the elevations in the papillae, as well as the ridges 

 left in the intervals between them. Fine tubular prolongations are continued from 

 this layer into the ducts of the sudoriferous and sebaceous glands. 



