200 PHYSIOLOGY AND MORPHOLOGY OF ANIMALS. 



General Structure of the Skin.— The skin con- 

 sists of two parts — dermis and epidermis. The dermis 

 consists of fibers crossing one another in all directions, 

 and, as it were, felted together. It is very strong and 

 very highly organized, full of blood vessels and nerves. 

 The epidermis contains no blood vessels or nerves, and 

 is not organized at all. It consists wholly of epithelial 

 cells; living nucleated cells in contact with the dermis, 



Fig. 127. — Section through the epidermis (ep) and the dermis (d) : n, nerves 

 of touch terminating in tactile corpuscles. 



but becoming more lifeless and flatter as we go from the 

 dermis to the surface, where they continually pass off as 

 scales or scarf. The nerve fibers come to the epidermis, 

 but do not penetrate it. They terminate near some of 

 the cells of the lowest layer (Fig. 127). 



Special Organ of Touch. — Wherever the skin is 

 specially organized for touch it is thrown into ridges, 

 as on the finger tips, or else rises into papillae, as on 

 the tongue (Fig. 128). In the case of ridges there is a 

 row of tactile corpuscles or bulbs in each ridge; in the 



