FIG. 301. 



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264 NORMAL HISTOLOGY. 



conveyed to the epidermis by means of migratory cells. The dark 

 tint of the skin of the negro and of other colored races depends 

 almost entirely upon the pigment within the epidermis, since in 

 the adult integument the subepithelial tissue contains comparatively 



few pigmented cells. While micro- 

 scopical examination shows the pres- 

 ence of pigment some weeks before 

 birth, the dark color is usually not 

 evident until a day or two after- 

 wards, owing to the opaque layer 

 of moist superficial scales which 

 masks the underlying colored cells. 

 The coriurn, derma, or true 

 skin consists of a felt-work of bun- 

 dles of white fibrous connective tis- 

 sue, with which elastic fibres and 

 non-striped muscle are mingled in 

 varying amounts. The corium is 

 densest in its outer part, where be- 

 neath the epidermis it is beset with 

 papillae, which greatly extend the 

 sensory surface and form the prin- 

 cipal organ of tactile sensibility. 

 The deeper parts of the corium are 

 much looser in structure, since the 

 bundles are coarser and more 



loosely disposed, fading away into the subcutaneous tissue. These 

 differences have led to the recognition within the corium of an outer, 

 denser stratum papillare and an inner, looser stratum reticulare ; 

 no sharp demarcation exists between the two, the papillary layer 

 blending with the reticular, while the latter in turn passes gradually 

 into the tissues of the subcutaneous stratum. 



The papillae vary in size, number, and disposition in different 

 regions, being best developed and most numerous on the palmar 

 surface of the hands and the fingers and on the corresponding parts 

 of the feet, where they attain a height of .25 mm.; on the other 

 hand, the papillae may be very slightly developed or even absent. 

 These elevations consist of closely-arranged bundles of fibro-elastic 

 tissue, and support the vascular loops together with the rich ter- 

 minal nerve-supply ; in certain localities the latter includes the 

 highly- specialized tactile corpuscles of Meissner, the corpuscles of 

 Vater, and the various end-bulbs which already have been described 

 in Chapter VI. The simplest type of the papillae is the rounded 

 or blunted conical elevation, but very often such projection becomes 



' ' ' 



Section of negro's skin, including epidermis 

 (a) and papillary layer of corium (b) ; the 

 deepest layers of epidermis (c) contain the 

 pigment. 



