690 NERVOUS SYSTEM. (Nervous Centres. Tar Encepnaton.) 
Fig. 390. 
Superior surface of the cerebellum, 
A, the square lobe; P, the posterior superior lobe ; S, superior layer of the crus cerebri ; 
q, tubercula quadrigemina ; /, Jocus niger; é, inferior layer of the crus cerebri. 
terior lamine form the floor of the posterior which the hemispheres are subdivided on the 
notch: the anterior form, by their adhesion inferior surface. 
to each other, the layer known by the name These segments may be very readily 
of valve of Vieussens, which fills up the interval guished from each other, and the names 
between the processus cerebelli ad testes. the accurate Reil has given them are 
The lamine which form the superior surface ciently appropriate. By separating each se 
of the median lobe, (or the superior vermiform ment from the adjacent ones and tracing i 
process,) are considerably fewer than those of lateral relations, the anatomist may form 
the hemispheres. This explains the less depth _ better idea than by any other means of they 
of the median lobe, when measured from before in which this portion of the cerebellum is 
backwards, than of the hemispheres. Two or nected with the hemispheres. . 
more of the lamine of the latter are united to The anterior extremity of the inferior’ 
a single lamina of the former, and thus the form process projects into the cavity of the foi 
superior vermiform process serves as a trans- ventricle, and serves to close it at its inferic 
verse commissure to the superior lamine of the tremity. Itisa pointed process, 
hemispheres. versely, continuous by its base with the res 
The inferior surface of the median lobe, or the vermiform process. Reil has named it 
inferior vermiform process, is likewise com- Nodule. From either side of it a valve 
posed of lamine, which take a transverse di- membrane of exquisite delicacy extends for 
rection and present a free convex border, with and outwards towards a lobule which is 
some resemblance to the rings of a worm in tached to each crus cerebelli near to the or 
action. ( Fig.391.) These laminearenotall of of the auditory nerve. These membranes 
equal transverse extent. The middle and pos- semble very much in shape the semi 
terior are the broadest; the anterior gra- valves of the aorta. By their attached mar 
dvally diminish in size. Hence the body which _ they adhere to the crus cerebelli, and their 
results from the conjunction of all the lamina margin projects into the cavity of the 
has a triangular form, its apex being anterior ventricle. eir inner extremities adhere to 
and its base posterior, corresponding to the nodule, and are connected to each other 
notch between the hemispheres. The lamine thin membrane of precisely similar te) 
which occupy its middle have a greater depth which is a commissure to them. Reil give 
than the rest, and consequently the body is the two membranes and their intermediate ¢ 
more prominent at this situation. necting one the name of posterior medul 
Certain deep fissures divide the inferior ver- velum.* The lateral membranes were first 
miform process into segments which evidently —* The valve of Vieussens is the anterior me 
correspond with and connect the lobes into  Jary velum. or 
