200 THE EVOLUTION OF MAN. 



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

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

 the contrary, consists principally of connective or fibrous 



i 



IB FlG - 212.— Human skin 

 \J3t=I in perpendicular section 

 ^ (after Bcker), much en- 

 ' Ml ' '' "' ' ' '$S§ larged : a, horny stratum of 

 : ^ffl outer-skin (epidermis) ; 6, 

 i ,(3j§ mucous stratum of outer- 

 EC- : ■ t{ skin; c, papillae of the 



I 



leather-skin (corium) ; d, 

 blood-vessels of the latter ; 

 e, f, excretory ducts of the 



ffi - ,,. sweat-glands (g) ; h, fat- 



globules of the leather-skin ; 

 -_ <\ i, nerve, passing above into 



| a touch-body. 



m~ m 



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-skin. In 

 its deeper part, the " subcutis" 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 papillse, contain the most delicate of all the sensory 

 organs of the skin, the "corpuscula tactus" Other papillae 



