SKIN. 



[ 580 ] 



SKIN. 



cells, and two distinct layers are recognized 

 in it (fig. 648), an inner forming the rete 

 mucosum (fig. 648 c), and an outer or cuticle 

 (fig. 648 d). The rete mucosum is softer 

 than the cuticle, and is frequently of a brown- 

 ish colour, from its cells, especially the 

 deepest, containing granules of pigment. 

 These cells are not all of the same form, 

 those immediately applied to the cutis being 

 somewhat elongated and arranged perpendi- 

 cularly upon its surface (fig. 648 6), the next 

 being roundish, and those nearest the cuticle 

 becoming longer, horizontally flattened, and 

 polygonal from mutual pressure (fig. 648 c). 



The cells of the cuticle are colourless, 

 flattened, often wrinkled or folded, and cor- 

 respond to the pavement epithelium of the 

 mucous membranes. Between the epidermis 

 and the cutis is situated a basement mem- 

 brane, which is rarely distinguishable. 



In the examination of the skin, sections 

 must be made with Valentin's knife, and 

 these treated with acetic acid, solution of 

 potash, dilute nitric acid, &c. The blood- 

 vessels are well seen as regards general 

 arrangement in injected preparations, some 



Fig. 648. 



Perpendicular section of the skin of the negro. a,papillae 

 of the cutis ; b, deepest and most intensely coloured layer 



of elongated perpendicular cells of the rete mucosum ; 

 c, upper layer of the rete ; 



d, cuticle. 

 Magnified 250 diameters. 



Fig. 649. 



a- 



Under surface of the epidermis of the palm of the hand, a, ridges corresponding to the furrows between the ridges 

 of the cutis ; ft, ridges corresponding to the furrows between the rows of papillae ; c, sudoriparous ducts ; d, their broad 

 insertions in the epidermis ; e, depressions corresponding to the papillae. 



Magnified about 20 diameters. 



