420 THE PACINIAN BODIES. 



devoted to the special senses, may be regarded as concerned in this func- 

 tion. The papilla? contain an elastic substance axile body, as it is term- 

 ed w hich serves to heighten the sense, and the yielding structure of the 



skin aids in the same effect. The papilla? are covered over with the cuti- 

 cle, through which, therefore, all *** 204 - 

 action on them must take place. 



Fig. 203. 



Simple papillae, magnified 35 diameters. Compound papillae, magnified 60 diameters. 



Fig. 203 (Todd and Bowman) represents simple papilla? of the palm, 

 the cuticle having been detached. Fig. 204 (Kolliker), compound papil- 

 ke, with two, three, or four points : a, base of a papilla ; #, , , separate 

 processes ; c, c 9 c, processes of papilla? whose bases are not visible. 



The mode in which the nerve fibre terminates in the papilla is as yet 

 The Pacinian doubtful, some asserting that it is arranged as a returning 

 bodies. loop, and some that it is by a pointed extremity. This lat- 



ter mode is thought to be illustrated by the structure of the bodies term- 

 ed Pacinian, which are ovoid in form, -^ to -^ of an inch in length, -^ to 

 -g 1 ^ in breadth, and attached by a pedicle to many of the cerebro-spinal 

 and sympathetic nerve branches. Each consists of many concentric 

 membranous layers, arranged like the coats of an onion, the interior ones 

 closer than the exterior. They have a central cavity, distended by a 

 fluid, which also intervenes between the coats. Across this cavity, and 

 occupying exactly its axis, a nerve fibre, which has cast off its white 

 sheath, passes, terminating at the other end either in branches or a knob. 

 The use of these bodies is wholly unknown, and even their structure is 

 doubtful, the existence of the central liquid referred to being denied by 

 some anatomists. 



The sensitiveness of a part is in proportion to the number of papilla? 

 The sensitive- ** contams - Tables have been constructed setting forth the 

 ness of differ- relations of different regions, as determined by placing a pair 

 regions. Q com p asseSj t j ie p i n t s O f which were covered with cork, on 

 the parts to be tried, the eyes being shut, and closing the compasses un- 

 til the pieces of cork could no longer be distinguished as separate. It 

 appears that this will take place on the tip of the tongue when the points 

 are the -^ of an inch apart ; on the tip of the third phalanx, at the -fa 

 of an inch ; on the lips, the one sixth of an inch ; tip of the great toe, 

 half an inch ; the lower part of the occiput, 1 inch ; and on the middle 

 of the thigh, 2 J inches. 



No part of the skin is entirely devoid of sensitiveness, as Kolliker has 



