558 
former was small, and possessed a forward direction. The latter 
was much larger, and at first sight appeared to be the only surface 
which the cerebellum possessed. It was directed more or less up- 
wards and backwards. The separation between the two surfaces was 
indicated by a slight ridge which corresponded to the line of attachment 
of the tentorium to the occipital bone. As far as this line the cere- 
brum extended posteriorly. The anterior surface of the cerebellum 
was thus in relation, through the tentorium, with the cerebrum. 
Owing to the limited area of this surface, the amount of cerebrum 
in relation to it was necessarily extremely small, and might be con- 
sidered as little more than the posterior edge of the cerebral hemi- 
spheres. Neither in the rabbit nor guinea-pig could the corpora 
quadrigemina be seen, until the cerebral hemispheres were drawn on 
one side, or the cerebellum pushed back. In the rat, the hemispheres 
of the cerebrum were in relation to those of the cerebellum ; but, in 
the middle line, owing to their divergence from each other at the 
posterior end of the great longitudinal fissure, the upper aspect of 
the corpora quadrigemina could be seen. When a bird’s-eye view 
of the brain was made, a large proportion of cerebellum was exposed 
lying behind the cerebrum, but this exposed surface was the occipital. 
Tiedemann, in his “ leones,’’ has illustrated the anatomy of the 
brain of the Rodentia, by figures of the brains of the agouti ( Cavia 
agouti ), porcupine, and beaver. In every instance he has repre- 
sented the cerebrum lying so far in front of the cerebellum as not 
to be in contact with it. Thus, exposure of the corpora quadrige- 
mina is occasioned. From my dissections I am satisfied that this 
mode of depiction does not give a faithful representation of the re- 
lation of the structures. The error has evidently arisen from 
studying the parts after removal from the cavity, and without taking 
properly into consideration the relations which they bore to each 
other in situ. 
Of the Insectivora, I have dissected in situ the brains of the 
mole and hedgehog. Of the Cheiroptera, I have dissected but one 
species. In these animals the surfaces of the cerebellum had about 
the same relation, as regards direction and size, as in the Rodentia. 
In all, the small tentorial surface was in apposition with little more 
than the posterior edge of the cerebrum. In none of the animals 
examined could the corpora quadrigemina be seen until the cere- 
bral hemispheres were turned on one side. 
