EXCRETION AND THE EXCRETORY ORGANS 475 



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. 



x a 



Fia. 141. A section through the epidermis, somewhat diagrammatic, highly 

 magnified. Below is seen a papilla of the dermis, with its artery, /, and veins, g g; 

 a, the horny layer of the epidermis; b, the rrtc mucosum or Malpighian layer; d, the 

 layer of columnar epidermic cells in immediate contact with the dermis; h, the 

 duct of a sweat-gland. 



The Corium, Dermis, or True Skin, Fig. 142, 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. 



