97 
the old and new world apes and monkeys, and the Lemurs. 
Every Lemur which has yet been examined, in fact, has its 
cerebellum partially visible from above, and its posterior lobe, 
with the contained posterior cornu and hippocampus minor, 
more or less rudimentary. Every Marmoset, American 
monkey, old world monkey, Baboon, or Man-like ape, on the 
contrary, has its cerebellum entirely hidden, posteriorly, by the 
cerebral lobes, and possesses a large posterior cornu, with a 
well developed hippocampus minor. 
In many of these creatures, such as the Saimiri (Chrysothriz), 
the cerebral lobes overlap and extend much further behind 
the cerebellum, in proportion, than they do in man (Fig. 17)— 
and itis quite certain that, in all, the cerebellum is completely 
covered behind, by well developed posterior lobes. The fact 
can be verified by every one who possesses the skull of any old 
or new world monkey. For, inasmuch as the brain in all mam- 
mals completely fills the cranial cavity, it is obvious that a cast 
of the interior of the skull will reproduce the general form of 
the brain, at any rate with such minute and, for the present 
purpose, utterly unimportant differences as may result from 
the absence of the enveloping membranes of the brain in the 
dry skull. But if such a cast be made in plaster, and com- 
pared with a similar cast of the interior of a human skull, 
it will be obvious that the cast of the cerebral chamber, re- 
presenting the cerebrum of the ape, as completely covers over 
and overlaps the cast of the cerebellar chamber, representing 
the cerebellum, as it does in the man (Fig. 21). A careless 
observer, forgetting that a soft structure like the brain loses 
its proper shape the moment it is taken out of the skull, 
may indeed mistake the uncovered condition of the cere- 
bellum of an extracted and distorted brain for the natural 
relations of the parts; but his error must become patent 
even to himself if he try to replace the brain within the 
cranial chamber. To suppose that the cerebellum of an ape 
is naturally uncovered behind is a miscomprehension com- 
parable only to that of one who should imagine that a mau’s 
H 
