CHAP, ix THE SKIN AND CUTANEOUS GLANDS 481 



vera, or coriuni) ; the former corresponds with the epithelium, the 

 latter with the areolar substrate of the mucous membranes, which 

 are an invagination of the skin. 



Both in the epidermis and in the derma several layers can be 

 distinguished: in the first, the harder, horny layer (stratum 

 corneum), and the softer, mucous or Malpighian layer (rete 

 mucosum) ; in the second, the corium proper, and the panniculus 

 adiposus (Fig. 129). 



From the physiological point of view it is an important fact 

 that the many layers of cells which make up the epidermis, from 



^-cc 



t o 



f- 



FIG. 129. Vertical section of skin and subcutaneous tissue, from the end of the thumb, across the 

 ridges and furrows. (Kolliker.) 20 diameters, a, horny ; b, Malpighian layer of epidermis ; 

 c, corium ; d, panniculus adiposus ; e, papillae on the ridges ; /, fat clusters ; g, sweat glands ; 

 h, sweat ducts ; i, their openings on the suriace. 



the deepest stratum of the Malpighian layer (which fit into the 

 surface of the corium) to the most superficial of the horny layer, 

 undergo perpetual modifications in their form and physico- 

 chemical characters, corresponding with so many alternating 

 phases of their existence. The deepest layer is the youngest, and 

 consists of cells vertical to the surface of the corium, to which 

 they are attached by denticulations at their lower ends (Fig. 130). 

 The next and older layers consist of rounded or polyhedral cells, 

 and become more flattened as they approach the surface. All these 

 cells have fine intercellular processes or bridges, which, if viewed 

 separately, give an effect of spines (the so-called " spiny cells "). 



VOL. II 2 I 



