THE SKIN. 197 



a variable amount of fat, but more compactly disposed in the super- 

 ficial portions, where it comes in contact with the epidermis, into 

 which it projects in the form of papillae. Some of these papillae 

 contain loops of capillary bloodvessels, while others are occupied 

 in their centres by peculiar nerve-endings, called " tactile corpus- 

 cles." In some situations, notably upon the palms and soles, the 

 papillae of the corium are arranged in rows. In most parts of the 

 skin they are irregularly scattered over the surface of the corium 

 (Fig. 173). 



The epidermis (Fig. 174) is a layer of stratified epithelium in 



FIG. 174. 



Vertical section of the epidermis of the finger. (Ranvier.) a, stratum corneum, or horny 

 layer ; b, stratum lucidum ; c, stratum granulosum ; d, rete mucosum ; e, " prickles " on 

 the cells bordering on the corium, which is not represented. 



which the cells multiply, where they are situated near the corium, 

 and gradually suffer a conversion into horny scales as they are 

 pushed toward the surface, where they are eventually desquamated. 

 The changes the cells undergo in their journey from the deeper 

 layers of the epidermis to its surface cause variations in their 

 appearances which have occasioned a division of the epidermis into 

 a number of more or less well-defined strata. The deepest stratum, 

 where the cells multiply and grow, is called the " rete mucosum." 

 It is composed of cells which gradually enlarge, becoming rich in 

 cytoplasm, and are connected with each other by minute cytoplas- 

 mic " prickles," between which there is a space affording a channel 

 for the circulation of nutrient fluids (Fig. 39). Above the rete 

 mucosum the cells appear more granular, owing to the formation 



