THE NERVOUS SYSTEM 



437 



as to whether they penetrate the dentine. In addition to such com- 

 paratively simple nerve endings, there are also found in the skin 

 and mucous membranes, especially where sensation is most acute, 

 much more elaborate terminations. These may be classified as^^(i) 

 tactile cells, (2) tactile corpuscles, and (3) end bulbs. 



Fig. 303. — Nerves and Nerve Endings in the Skin and Hair Follicles. (After G. 

 Retzius.) As, Outer root sheath; c, most superficial nerve-fibre plexus in the cutis: 

 dr, sebaceous glands; //, the hair itself; list, stratum corneum; is, inner root sheath of 

 hair; n, cutaneous nerve; rm, stratum germinativum Malpighii. 



A simple tactile cell is a single epithelial cell, the centrally di- 

 rected end of which is in contact with a leaf-like expansion of the 

 nerve terminal, the tactile meniscus. In the corpuscles of Grandry, 

 found in the skin of birds, and in Merkel's corpuscles, which occur 

 in mammalian skin, several epithelial cells are grouped together to 



