TIIR NERVOUS SYSTEM 



439 



These terminal fibrils usually end in a flattened expansion consisting 

 of neurofibrils and perifibrillar substance. Tactile corpuscles are 

 also found on the volar surface of the forearm, eyelids, lips and 

 tip of the tongue. 



Of the so-called end bulbs, the simplest, which are found in the 

 mucous membrane of the mouth and conjunctiva, consist of a central 

 core formed by the usually more or less 

 expanded end of the usually branched axis 

 cylinder, surrounded by a mass of finely 

 granular, nucleated protoplasm — the inner 

 bulb — the whole enclosed in a capsule of 

 flattened connective-tissue cells continuous 

 with the sheath of Henle. Other end 

 bulbs may be compound. End bulbs are 

 found also in the mucous membrane of the 

 tongue, epiglottis, nasal cavities, lower 

 end of rectum, peritoneum, serous mem- 

 branes, tendons, Hgaments, connective 

 tissue of nerve trunks, synovial mem- 

 branes of certain joints and external geni- 

 tals, especially the glans penis and cHtoris.^ 



The Pacinian bodies (Fig. ^^07) are 

 laminated, elliptical structures which differ ^^^ aoy.-Pacinian Body 

 from the more simple end bulbs already from Mesentery of Cat. (Ran- 



... i J 1 vier.) c, Lamina of capsule; 



described, mainly in the greater develop- (/, epithelioid cells lying between 

 ment of the perineural capsule. The cap- ifmin^ of capsule; n, nerve 



tr IT 1 fibre, consistmg of axis cyimder 



sule is formed by a large number of con- surrounded by Henle's sheath, 



, • 1 11 11 11 • 4-* ™ ^c enterins; Pacinian body; /, 



centric lamelte, each lamella consisting of perineural sheath; m, inner 



connective-tissue fibres Hned bv a single bulb; n, terminal fibre which 



, breaks up at a mto an irregular 

 layer of flat connective- tissue cells. ihe bulbous terminal arborization. 



lamellaj are separated from one another 



by a clear fluid or semifluid substance. As in the simpler end 

 bulbs, there is a cyHndrical mass of protoplasm within the cap- 

 sule known as the inner bulb. Extending lengthwise through 

 the centre of the inner bulb and often ending in a knob-like ex- 

 tremity is the axis cylinder. Arteries in the vicinity of the cor- 

 puscle break up into capillary networks surrounding the corpuscle. 



1 This description of the distribution of the various receptors is principally taken 

 from the excellent account in Schafer's "Text-Book of Microscopic Anatomy." An 

 admirable and still more detailed account is to be found in "The Nervous System," 

 by Barker. 



