SKIN. 



[ 607 ] 



arranged perpendicularly upon its surface 

 (tig. 643 b). The next fire so;nnvhat cubi- 

 cal; and their surface often exhibits fiat 

 ->s or teeth, forming the so-called 

 " prickle-cells." The cells of the next rows 

 are polygonal, and contain one or more 

 nuclei ; "tliey have a distinct cell-wall, and 

 some have hair-like processes. 



The cells of the cuticle are colourless, 

 tl.itt 'tied, often wrinkled or folded, and 

 correspond to the pavement epithelium of 

 the mucous membranes. Between the epi- 

 dermis and the cutis is situated a basement 

 membrane, which is easily distinguishable. 



In preparing the skin, it may be hardened 

 by a mixture of chromic acid and alcohol, 

 and stained with picro-carmiue. By keep- 

 ing a portion of skin in a digestive liquid, as 

 pepsine and dilute muriatic acid, the con- 

 ne tive tissue becomes transparent, and ex- 

 hibits clearly the muscular and elastic fibres. 



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 



SKIX. 

 Fig. 643. 



Perpendicular section of the skin of the Negro, a, 

 papillae of the cutis; 6, deepest and most intensely 

 coloured layer of elongated perpendicular cells of the 

 rete mucosum ; c, upper layer of the rete ; d, cuticle. 



Magnified 350 diameters. 



Fig. G44. 



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

 d^ .of the cutis; b, ridges corresponding to the furrows between the rowsof papilla 

 , their broad insertions in the epidermis; e, depressions corresponding to the papilla.'. 



Magnified about 20 diameters. 



