CENTRAL NERVOUS SYSTEM IN VERTEBRATE ANIMALS. 
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The intermediate layer of Purkinje cells follows the folds and involutions of the 
molecular layer, except a small tract along the central line of the dorsal portion. In 
it are seen not only the true characteristic Purkinje cells, but also smaller cells; 
between the two there is a gradation in size. 
The larger Purkinje cells (fig. 21) are about 27/a long by lip, broad, and the smaller 
15 p by 10p ; they are generally elongated and triangular in shape; two molecular 
processes are given off from the side turned towards the molecular layer, and one 
finer process from the narrower end is directed towards the granular layer. Occasionally 
these cells are broader at the end turned towards the granular layer, as if they had 
been truncated ; sometimes fusiform cells are found with a process emerging from 
each extremity, resembling those found in Teleostei. The processes which pass into 
the molecular layer may often be traced nearly as far as the external surface, their 
course is nearly direct, and they give off branches which preserve the same general 
direction as the main trunk ; they thus contribute to a greater extent to the striation 
of the molecular layer than in Mormyrus. The smaller cells mentioned above are 
found in the neighbourhood of the Purkinje cells, and their processes join the 
fibrillar network of the molecular layer. 
The outer or molecular layer of the cerebellum (fig. 21) consists, in addition to the 
processes of the Purkinje cells, also of a fibrillar network, the general tendency of 
the striation of which is in a longitudinal direction ; the fibrils composing this are 
not so broad as those which go in a course perpendicular to the surface. Near the 
external edge the network becomes irregular. Cells of small size are found sparingly 
scattered through the central and outer portions of the layer; they are more 
numerous than in Mormyrus, and still more so than in Mugil Oephalus, in which 
they were seldom found; they are rather larger in size than in the Teleostei, 
averaging 6p or 7p in diameter ; they are spherical or sometimes slightly triangular 
in shape, and give off processes on all sides which join, some the longitudinal and 
some the radial fibrils. In Phina they appear to be fewer in number, but somewhat 
larger than in the other species examined. In other respects this description applies 
equally to all. 
The ventricle of the cerebellum is lined by a layer of endothelium derived from the 
general endothelial lining of the brain cavities. 
Restiform Bodies. 
The crura cerebelli (fig. 12) in their descent on to the medulla oblongata, are accom¬ 
panied by the molecular and granular layers, which extend in Paja nearly as far as 
the posterior end of the fourth ventricle ; so that the tuberosities which bound that 
ventricle laterally appear as if they were the continuation of the cerebellum; the 
absence, however, of the Purkinje cells marks a substantial difference in organization ; 
for these cells may be considered as characteristic of the cerebellum, structures more 
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