STRUCTURE OF THE PACINIAN CORPUSCLES. 135 
The Structure of the PAcINIAN CoRPUSCLES CONSIDERED 
with REFERENCE to the HomotoGizs of the SEVERAL 
PARTS COMPOSING THEM. By Epwarp ScHAFER, Assis- 
tant-Professor of Physiology in University College, 
London. (With Plates VIII and IX). 
SrupIEpD generally, a Pacinian corpuscle may be looked 
upon as consisting of three parts—the central fibre, the core, 
and the capsular enclosure. I propose in the first place to note 
down the result of observations upon the structural appear- 
ances presented by each of these parts, as ordinarily met 
with, without entering into the consideration of the variations 
which present themselves more than may seem necessary for 
the elucidation of the structure; and then to discuss briefly 
the homologies which the component parts of the Pacinian 
corpuscle severally bear to the parts which compose the 
entering nerve, at the same time indicating the manner in 
which the structures of the one appear to become continued 
into those of the other. 
The observations were in all cases made upon the Pacinian 
corpuscles from the cat’s mesentery ; these having been selected 
on account of the facility with which they are obtainable in 
the fresh condition, combined with the fact that, according to 
the unanimous testimony of observers, their structure differs 
in no essential particular from that of the corpuscles met 
with on the nerves of various parts of the human body. 
The Central Fibre. 
As first shown by Grandry, this presents a distinct appear- 
ance of fibrillation, the fibrils, as a rule, crossing one another 
very obliquely (see Plate VIII, fig. 2, ef) ; thus rendering it 
difficult or impossible to trace each separate fibril through- 
out its whole length. ‘The central fibre is uniform in size 
except towards its extremity, where most commonly it be- 
comes enlarged; but sometimes there is no distinct swelling, 
the fibre being merely marked at its sides with minute den- 
ticulations or projections, from which, in preparations stained 
with chloride of gold, fine fibrils occasionally appear to pro- 
ceed outwards. (In one instance the central fibre terminated 
abruptly after traversing only two thirds of the length of the 
core, by a rounded extremity, uniform in diameter with the 
rest of the fibre.) ‘The terminal enlargement, when present, 
varies much both in size and shape, in some cases having a 
simple rounded outline, in others an irregular shape, with 
