CHAPTER 1 



MINUTE ANATOMY OF THE PAPILLARY RIDGES AND 

 PAPILLA OF THE CORIUM 



The minute anatomy of the human skin has been very fully 

 investigated and described elsewhere, and it is only necessary 

 here to allude to those structures of the sldn which especially 

 concern our subject. The five strata of the superficial layer, 

 or epidermis, need no detailed description. The three strata 

 of Hving cells composing the rete mucosum or malpighian layer 

 lie more deeply, the two superficial strata being formed of dried 

 epithelial cells. In the various sections of the mammahan skin, 

 which will be shown later, the rete mucosum is a very prominent 

 feature because of its being that portion of the skin in which 

 pigment is developed. The epidermis, developed from the 

 outer layer of the epiblast, is moulded on the surface of the 

 corium which is studded with papillae, thus the two main struc- 

 tures of the skin are developed from different embryonic layers, 

 the corium being formed from the mesoblast. 



The corium is an extremely dense structure composed of 

 areolar tissue the outer portion or papillary layer being very 

 dense, whereas the reticidar layer is more lax and the fibres are 

 felted together less firmly and pass imperceptibly into the sub- 

 jacent connective tissue and fat. The most notable part of 

 the corium is that row of papillae which irregularly stud its 

 surface. The relation of these to the epidermis is well seen 

 when a piece of skin is macerated, in which case the two layers 

 are separated from one another and the projecting papillae are 

 seen on the corium, and on the deeper surface of the epidermis 

 small pits corresponding to the papillae. 



In man the papillae are large and closely set on the palmar 



