5.8.5 
Houser, Zhe Neurones of a Selachian. 109 
to their presence here is due, in part, the marked striation per- 
pendicular to the surface which is so characteristic of the super- 
ficial zone. 
The axone always arises from the base of the cell-body, 
and it pursues a horizontal course for some distance. It then 
turns downward through the granular layer to enter the system 
of fibres leaving the cerebellum. Where the granular layer is 
absent, the axone may be traced into the layer of basal fibres 
for a still greater horizontal course. The axone is remarkable 
for the fact that it does not give off collateral branches. 
The cell-body appears to have its form determined quite 
largely by the number and disposition of the dendrites arising 
from it. It may be rounded, oval, or even triangular in out- 
line. The longer axis of the cell, while usually perpendicular 
to the surface of the fold, may be oblique or still farther tilted 
over from the orientation characteristic of it for the higher ver- 
tebrates. Even the size of the cell is influenced by its position. 
The diameter is greatest in those cells lying at the part of the 
fold where the side curves abruptly into the summit. On the 
sides of the fold, the size is remarkably less, and the dendrites 
pass outward at a wider angle, often causing the cells here to 
assume a horizontally elongated form. The cell studied by 
SZCZAWINSKA (’98) evidently was of this latter type. 
The internal structure of the PURKINJE cell is demonstrated 
less readily with methylen-blue than is the case for most nerve- 
cells of Mustelus. In successful preparations, however, the 
cytoplasm is found to hold tigroid masses of triangular or spin- 
dle-shaped form. These bodies are neither large in size nor 
many in number. There are always several of the greatest 
. diameter arranged near to and concentric with the nuclear mem- 
‘brane. The -thick bases of the dendrites have small, narrow, 
lenticular tigroids distributed sparingly as far as the level of the 
first. great branches. The character and distribution of the 
tigroid-bodies will be seen by reference to Fig. 49. 
The nucleus of the cell lies in a basal position, but it is 
always bordered by some little thickness of cytoplasm. The 
form is oval or circular, with an almost even contour. There is 
; 
