pacijS^iax bodies. 



151 



FiL'. 104, 



neurilemma, with connective tissue and one or more fine blood-vessels ; 

 it joins the corpuscle at or near one end, and conducts the nerve-fibre 

 into it. The Uttle body itself, examined under the microscope, is found 

 to have a beautiful lamellar structure (fig. 103, a). It consists, in fact, 

 of numerous concentric membranous capsules encasing each other like 

 the coats of an onion, with a small quantity of pellucid fluid included 

 between them. Surrounded by these capsules, and occupying a 

 cylindrical cavity in the middle of the corpuscle, is the core, formed of 

 transparent and homogeneous soft substance, in the midst of which the 

 prolongation of the nerve-fibre is contained. The number of capsules 

 is various ; from forty to sixty may be counted in large corpuscles. 

 The series immediately following the central or median cavity, and 

 comprehending about half of the 

 entire numbei', are closer together 

 than the more exterior ones, seeming 

 to form a system by themselves, 

 which gives rise to a white streak 

 often distinguishable by the eye 

 along the middle of the corpuscles 

 when seen on a dark ground. Out- 

 side of all, the corpuscle has a coating 

 of ordinary connective tissue. The 

 capsules, at least the more superficial 

 ones, consist each of a thin lamella 

 of an almost homogeneous or faintly 

 striated appearance, with a reticulum 

 of exquisitely fine fibres, probably of 

 an elastic nature, on the outer 

 surface. On the inner surface of 

 each lamella a number of clear 

 oval nuclei are to be seen, and 

 treatment with nitrate of silver 

 shows these to belong to a delicate 

 layer of flattened epithelioid cells 

 (fig. 10-1), lining each successive 

 capsule (Hoyer). It is thus seen 

 that in intimate structure the cap- 

 sules correspond very closely to the 

 lamellse of v/hich the neurilemma of 

 the nerve, before described, is com- 

 posed. 



The nerve fibre, the disposition 

 of which must now be noticed, is 

 conducted along the centre of the 

 stalk, enters the corpuscle, and passes 

 straight into the central cavity, at 

 the further end of which it termi- 

 nates. The neurilemma surrounding the nerve-fibre in the peduncle 

 accompanies it also in its passage through the series of capsules, 

 gradually decreasing in thickness as it proceeds, and ceasing alto- 

 gether when the nerve has reached the central cavity. According 

 to Pacini, the neurilemma forms a series of concentric cylindrical layers, 

 which successively become continuous with, or rather expand into the 



Fig. 104.— Pacinian Corpuscle from 

 Mesentery op Cat ; stained with 

 Nitrate of Silver. Magnified. 



The epitlielioid cells of tlie outermost 

 capsule are shown, and their continuity, 

 at the peduncle, with those of the cor- 

 responding layer of the neurilemma (from 

 a dra-ning by Mr. G. C. Henderson). 



