CHAPTEE LII 



CUTANEOUS SENSATIONS 



THE tactile end-organs are of numerous kinds, but the following are 

 the principal ones : 



Pacinian Corpuscles. These are named after their discoverer 

 Pacini. They are little oval bodies, situated on some of the cerebro- 

 spinal and sympathetic nerves, especially the cutaneous nerves of 

 the hands and feet, where they lie deeply 

 placed in the true skin. They also occur 

 on the nerves of the mesentery of some 

 animals like the cat. They have been ob- 

 served also in the pancreas, lymphatic 

 glands and thyroid glands, as well as in the 

 penis. They are about j 3 ^- inch long. Each 

 corpuscle is attached by a narrow pedicle to 

 the nerve on which it is situated, and is 

 formed of several concentric sheaths of con- 

 nective-tissue, each layer being lined by 

 endothelium (figs. 517, 518); through its 

 pedicle passes a single nerve-fibre, which 

 loses its medullary sheath and enters a 

 central core, at or near the distal end of 

 which it terminates in an arborisation. Some 

 of these layers are continuous with those 

 of the perineuriurn, but some are super-added. 

 In some cases two nerve-fibres have been 

 seen entering one Pacinian body, and in 

 others a nerve-fibre after passing unaltered 

 through one has been observed to terminate 

 in a second. 



The corpuscles of Herbst (fig. 519) are 

 closely allied to Pacinian corpuscles, except that they are smaller 

 and longer, with a row of nuclei around the central termination 

 of the nerve in the core. They have been found chiefly in the 

 tongues and bills of 'Iducks. 



719 



FIG. 516. Extremities of a nerve 

 of the finger with Pacinian cor- 

 puscles attached, about the 

 natural size. (Adapted from 

 Heiile and Kolliker.) 



