200 



THE EVOLUTION OF MAN. 



germ-layers from the skin-sensory layer, and, directly, from 

 the horn-plate of the latter. The leather-skin (corium), on 

 the contrary, consists principally of connective or fibrous 



Ftq. 212.— Human skin 



in [.erpendicular section 

 (aft CI Kcker), much en- 

 lar'_re<.i : a, horuy stratum of 

 uuLrt rkin (epidermiti) ; 6, 

 tuucuus stratum of outer- 

 skin ; c, papillae of the 

 leather-skin (corium) ; d, 

 biuud- vessels of the latter; 

 e, /, excretory ducts of the 

 sweat-ijlands (p) ; h^ fat- 

 globules of the leather-skin ; 

 i, nerve, passing above into 

 a touch -body. 



tissue, contains numerous blood-vessels and nerves, and has 

 a different origin. It develops from the outer stratum of 

 the second secondary germ-layer, from the skin-fibrous layer. 

 The leather-skin is much thicker than the outer-skm. In 

 its deeper part, the " aubcutis," lie many masses of fat-cells 

 (Fig. 212, h). Its upper part, the true " cutis," or papillary 

 layer, forms, over nearly the whole surface of the body, a 

 number of microscopic cone-shaped warts, or papillae, which 

 fit into the overlying epidermis (c). These touch-warts, or 

 sensory papillge, contain the most delicate of all the sensory 

 organs of the skin, the " corpwscula tactius" Other papillae 



