200 



THE EVOLUTION OF MAN. 



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

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

 the contrary, consists principally of connective or fibrous 



FIG. 212. Tinman skin 

 in perpendicular section 

 (after Ecker), much en- 

 larged : a, horny stratum of 

 outer-skin (epidermis) ; b, 

 mucous stratum of outer- 

 skin ; c, papillae of the 

 leather-skin (cormw) ; d, 

 blood-vessels of the latter ; 

 e, f, excretory ducts of the 

 sweat-glands (g) ; h, fat- 

 globules of the leather-skin ; 

 t, 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-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 papillae, contain the most delicate of all the sensory 

 organs of the skin, the " corpuwula tactus." Other papillae 



