64 



SKIN. 



Fig. 51. 



The skin consists of two layers, the true skin, also called cutis vera or 

 chorion, and the cuticle or epidermis. The cutis vera'' is the thicker 

 and deeper of the two: is white, and semi-transparent in all persons ; 

 its internal or inferior surface is much blended with the subjacent cellu- 

 lar tissue, and contains a number of pits or depressions ; the external 

 surface has a number of conical projections called pajnllce tactus^ 

 which are particularly numerous in those parts where there is much 

 motion. On the hands and feet they are arranged in spiral and 

 semicircular rows, which occasion a similar wrinkle of the cuticle. 

 They consist of an artery, vein and nerve ; 

 the sensibility of a part is in ratio to their 

 number. The skin itself is formed of con- 

 densed cellular tissue, the yellow fibrous 

 element predominating where great elasti- 

 city is required, as in the armpit; the 

 white element, where resistance is de- 

 manded, as in the sole of the foot. Between 

 the interstices of these fibres, pass innu- 

 merable vessels, ducts, &c., &c. It is 

 thickened by pressure ; boiling reduces it 

 to gelatine ; and tannin converts it into 

 leather. 



The cuticle or epidermis" affords pro- 

 tection to parts most exposed to pressure 

 or friction ; its thickness varies with the 

 amount of pressure to which it is sub- 

 jected ; compare the hand of an artisan 

 with that of a delicate female. It is rot per- 

 meated by vessels or nerves, but consists 

 of particles arranged in different laminse ; 

 those that are deepest are granular, those 

 of the next layer are more compressed, 

 whilst those upon the surface are mere 

 scales. These superficial scales, which 

 are horny, are constantly being shed, and 

 \^^^if(^^^^f/Wi "^^'^ particles constantly supplied by the 



9'^W/i^W)Jiwr^ lm\\ moist granules, which are below. The 

 laminated condition makes it easy to 

 divide into different layers, and the in- 

 ferior layer was formerly called by a dis- 

 tinct nnme,rete mvcosuni ; but it is nothing 

 more than the deepest or most recently 

 formed part of the cuticle, which also con- 

 tains the colouring matter, very abundan- 

 dant in moles, freckles, and the skin of 

 negroes. 



