938 
MR. A. SANDERS ON THE ANATOMN OE THE 
They have a tendency to be arranged in distinct rows, the spaces between which are 
occupied by nervous fibrilhe. 
There has been a good deal of dispute as to the nature of these cells. Some 
histologists think that they are connective tissue cells, others that they are nervous 
elements ; with these latter I must throw in my lot; there seems to be no manner of 
doubt but that they are nervous ; and it is difficult to imagine that a whole lobe of a 
brain should be almost entirely made up of connective tissue, or what object could be 
fulfilled by such an arrangement; it would not be required to support the few remain¬ 
ing elements which would then consist of little else than the Purkinje cells which one 
would suppose might be better packed up in a smaller compass. 
Valvula Cerebelli, 
I hope to prove eventually that the wings described at the commencement of this 
paper are nothing more than the lateral parts of the valvula cerebelli enormously 
developed; but for the present I will confine myself to a description of their structure. 
They consist of two parts : a central portion, which is simply a continuation of the 
cerebellum, containing precisely the same elements arranged in precisely the same 
manner; and a pair of wings. 
In many Fishes this part forms nearly the whole of the valvula cerebelli, the wings 
not being much developed ; but here, although it is much more extensive than in many 
Fishes in which it forms the greater part of the valvula, it occupies but a small portion 
of the entire structure. 
It consists of three tubercles (fig. 1) arranged one in front of the other, diminishing 
in size from behind forward; of these the most posterior appears actually to be part 
of the cerebellum. They each present the molecular, intermediate and granular layers. 
The first of these three layers can be traced continuously from the cerebellum over 
these tubercles and ends in front of the foremost with an undulating free edge as if 
an indefinite development of these bodies might take place. The wings arise from 
each side of this central portion and cover more or less the remaining lobes of the 
brain according to the age of the animal. The greater part of their mass is formed 
by an accumulation of minute cells which closely resemble those of the granular layer 
of the cerebellum ; with these are found numerous bundles of fibrillse. This accumula¬ 
tion of cells takes the form of thick plates which are bent and folded as formerly 
explained. On one side of these plates a series of closely arranged ridges are placed 
(fig. 3). Each of these ridges is a cerebellum in miniature and consists of the regular 
number of layers, the molecular, the granular, the intermediate, and the fibrous. 
They are so placed that the molecular layers of a pair of ridges are arranged in close 
contact, with only a process of the pia mater between them, then comes the granular 
and the intermediate, and finally the fibrous layer is interposed between a pair of 
ridges on the other side, one fibrous layer serving for two contiguous ridges ; the fibrillse 
