EXCRETION AND THE EXCRETORY ORGANS 531 



after an ordinary warm bath, are the dead outer scales of the 

 horny stratum of the epidermis. 



In dark races the color of the skin depends mainly on minute 

 pigment-granules lying in the cells of the deeper part of the Mal- 

 pighian layer. 



No blood or lymphatic vessels enter the epidermis, which is en- 

 tirely nourished by matters derived from the subjacent corium. 

 Fine nerve-fibers run into it and end there among the cells. 



The Corium, Dennis, or True Skin, Fig. 143, consists funda- 

 mentally of a close feltwork of elastic and white fibrous tissue, 

 which, becoming wider meshed below, passes gradually into the 

 subcutaneous areolar tissue (Chap. IV) which attaches the skin 

 loosely to parts beneath. In tanning it is the dermis which is 

 turned into leather, its white fibrous tissue forming an insoluble 

 and tough compound with the tannin of the oak-bark employed. 



Wherever there are hairs, bundles of smooth muscular tissue are 

 found in the corium; it contains also a close capillary network 

 and numerous lymphatics and nerves. In shaving, so long as the 

 razor keeps in the epidermis there is no bleeding; but a deeper cut 

 shows at once the vascularity of the true skin. 



The outer surface of the corium is almost everywhere raised into 

 minute elevations, called the papillce, on which the epidermis is 

 molded, so that its deep side presents pits corresponding to the 

 projections of the dermis. In Fig. 142 is shown a papilla of the 

 corium containing a knot of blood-vessels, supplied by the small 

 artery, /, and having the blood carried off from them by the two 

 little veins, g g. Other papillae contain no capillary loops but 

 special organs connected with nerve-fibers, and supposed to be 

 concerned in the cutaneous senses (Chap. XIII). On the pal- 

 mar surface of the hand the dermic papillae are especially well de- 

 veloped (as they are in most parts where the sense of touch is 

 r.cute) and are frequently compound, or branched at the tip. On 

 the front of the hand, they are arranged in rows; the epidermis fills 

 up the hollows between the papillae of the same row, but dips down 

 between adjacent rows, and thus are produced the finer ridges seen 

 on the palms. In many places the corium is also furrowed, as op- 

 posite the finger-joints and on the palm. Elsewhere such furrows 

 are less marked, but they exist over the whole skin. The epidermis 

 closely follows all the hollows, and thus they are made visible 



