398 STUDIES IN ADVANCED PHYSIOLOGY. 



terial. For this reason it has been termed the stratum 

 lucidum. 



It will therefore be observed that the epidermis is not at 

 all in any way derived from the dermis beneath. The der- 

 mis is fibrous, the epidermis cellular. The epidermis is 

 a result of the continued division of the Malpighian layer 

 of the epidermis, and when this layer is not present, as in 

 serious wounds, scalds or bruises, it is absolutely impossi- 

 ble for the epidermis to appear. Under such conditions at- 

 tempts are frequently made to graft portions of the Mal- 

 pighian layer from another body on to this spot, and if the 

 graft is successful the epidermis begins to grow from 

 these places by the proliferation of the Malpighian cells en- 

 grafted. These Malpighian cells are further of interest in 

 the fact that in them lie the pigments which characterize 

 the various races of mankind. A certain amount of pig- 

 ment also occurs in the cells above the Malpighian layer, 

 but it is much less pronounced, and the intense black of the 

 colored races, or the red of the -Indian is the color which 

 shines through the somewhat transparent epidermis from the 

 Malpighian layer at its base. 



2. Corium. The corium or true skin is the fibrous 

 part of the skin lying immediately beneath the epidermis. 

 It consists almost wholly of closely packed white fibrous 

 tissue, containing, however, a small amount of yellow elas- 

 tic fibers. In the meshes of these fibers are found con- 

 nective tissue corpuscles, imbedded nodules of fat, blood- 

 vessels and nerves, and finally the glands of the skin. 



The true surface of the corium is thrown up into pecu- 

 liar papillae sometimes simple, sometimes branched, which 

 project up into the epidermis. In these papillae thert lie 

 in some instances loops of blood-vessels, more generally 

 tactile corpuscles concerned in the sense of touch. These 

 papillae are arranged in defined rows, and as the epidermis 

 follows these papillae they show on the outside of the skin 

 as those peculiar lines and furrows so evident on the 



