576 



THE SKIN. 



windings have the characteristic corkscrew-like appearance. (See 

 Fig. 242.) 



(11) The nails are flattened, plate-like formations of a horny 

 or epidermal character. The skin is elevated along the lateral 

 borders of the nail, and produces at the posterior end of the nail 

 a broad pouch, termed the matrix, which incloses the root of the 

 nail. According to Unna, the matrix proper of the nail is only 

 the posterior portion of the derma, commencing with the ante- 

 rior curved line of the lunula ; and only the bottom of the fur- 

 row serves as a matrix to the anterior portion of the nail. H. 

 Hebra does not consider the lunula as a part of the matrix, for it 

 is destitute of papillae, and scantily supplied with blood-vessels 



FIG. 242. DUCT OF THE SWEAT-GLAND WITHIN THE 

 EPITHELIAL LAYERS OF THE SKIN. 



BP, papilla with injected Wood -vessels ; V, valley between two papillae; D, duct in tlie 

 rete mucosum ; EE, epidermal layer ; PL, coarsely granulated epithelia, deeply stained with 

 carmine ; P, duct with corkscrew windings in the epidermal layer. Magnified 200 diameters. 



The papillary layer of the skin subjacent to the nail is 

 highly developed, the papillae being arranged in parallel rows 

 corresponding to the long axes of the fingers and the toes. 

 The papillae are shallow in the region of the matrix, but increase 

 in size toward the free portion of the nail, especially toward its 

 lateral borders. At the inner surface of the lateral ledges, and 

 in the depth of the lateral furrow, they are replaced by the pa- 

 pillae of the skin. The derma forming the papillae is composed 

 of coarse, dense bundles, inclosing a comparatively small number 





