152 NEEVOUS TISSUE. 



capsules, the innermost, of course, advancing farthest. Others suppose 

 that the capsules are all successively perforated by a conical channel 

 ■which gives passage to the nerve Avith its neurilemma, but at the same 

 time has its own proper wall, round which, on the outside, the capsules 

 are attached. "VVe must, however, adhere to Pacini's view, having in 

 silvered preparations observed the layers of epithelioid cells lining the 

 capsules to be directly continuous with those of the neurilemma. 



The nerve-fibre is single, as it runs along the peduncle, unless when 

 the latter supports two corpuscles ; it retains its dark double contour 

 until it reaches the central cavity, where, diminished in size, and freed 

 from its perineurium, it becomes somewhat flattened, and presents the 

 appearance either of a pale, finely granular, and very faintly outlined 

 band or stripe, little narrower than the previous part of the libre, or of 

 a darker and more sharply defined narrow line; differing thus in appear- 

 ance according as its flat side or its edge is turned towards the eye. 

 The pale aspect which the fibre presents in the centre of the corpuscle 

 has with some probability been ascribed to its losing the white sub- 

 stance or medullary sheath on entering the cavity. Henle and Kolliker, 

 however, think that it is more likely the result merely of a diminution 

 in size, together with a certain degree of flattening. It sometimes 

 happens that the fibre regains its original magnitude and double con- 

 tour for a short space, and changes again before it terminates ; this is 

 especially liable to occur while it passes through a sharp flexure in a 

 crooked central cavity. The fibre ends by a sort of knob at the further 

 extremity of the median cavity, which is often itself somewhat dilated. 

 The knob, often finely granular, appears to be an expansion of the 

 axis-cylinder, and is sometimes of considerable size. It may.present an 

 irregular shape with processes branching outwards from the sides, and 

 in such cases has been taken to represent a nerve-cell ; but the 

 characteristic nucleus of the latter is absent. The ultimate destination 

 of the processes is unknown. The axis-cylinder presents the usual 

 longitudinal fibrillation as it passes through the core, and the fibrils 

 become somewhat spread out as they pass into, the terminal expansion. 

 In many cases the fibre, before terminating, divides into two branches, 

 as represented in figure 103, b. : a division into three has been observed, 

 but this is very rare. In case of division of the fibre, the cavity is 

 generally, but not invariably, divided in a corresponding measure, 

 and the inner capsules present a figure in keeping with it. It is 

 worthy of remark, that the nerve-fibre in its course along the cavity 

 runs almost exactly in the axis of the channel, and it maintains this 

 position even when passing through the abrupt flexures of an irregu- 

 larly shaped cavity. It sometimes happens that a fibre passes quite 

 through one corpuscle and terminates in a second, resuming its 

 original size and dark outline while passing from the one to the other ; 

 and it is said that a nerve-fibre may go through- two Pacinian 

 bodies without terminating in either, returning again to the parent 

 nerve in form of a loop (Pappenheim), Other varieties occur, 

 for an account of which the reader is referred to the several 

 authorities already mentioned. A little artery enters the Pacinian 

 bodies along with the nerve, and soon divides into capillary branches, 

 which run up between the capsules. They then form loops, and 

 return by a similar route into a vein corresponding to the artery: a 

 single capillary usually accompanies the nerve as far as the central 



