146 SKIN AND ITS APPENDAGES. 



rete mucosum of Malpighi. Finally, the third stratum 

 or horny layer, very variable in its thickness, is com- 

 posed entirely of scale-like cells, which overlie each 

 other regularly (fig. I. 2; fig. II. 1), and which differ 

 from the cells of the rete mucosum, not only in their 

 form, but also in the absence of their nuclei, and in 

 their contents, which are more or less opaque, and 

 coarsely granular. They resist also for -a longer time 

 the action of acetic acid, and caustic potash. 



The epidermis, like the other epithelial membranes, 

 has neither vessels nor nerves, but it does not, on this 

 account, possess in any less degree true organization 

 and indubitable vitality. 



Derma. The true skin is naturally divisible into two strata, 

 which insensibly mingle with each other along their 

 line of contact. The deep, or reticulated layer is 

 made up of a loose interlacement of connective and 

 elastic fibres which, on its internal surface, become 

 continuous with those which go to form the super- 

 ficial fascia. It is in this reticulated stratum of the 

 derma that we find its glands, the hair follicles, and 

 fat cells, grouped together in little rounded masses. 

 (PL XXIII. fig. I. 8, 10.) It is here also that its 

 blood-vessels ramify and give off their ultimate 

 branches, which are distributed to the superficial 

 layer. 



The surface of the superficial or papillary layer of 

 the true skin is studded with minute projections 

 known as its papillae. These papillae are not every- 

 where uniformly distributed, nor do they present 

 everywhere the same volume ; they are most numerous 

 and largely developed on the extremities of the fin- 



