Surgeons, the latter from the photograph of the cast of a Chimpanzee's
skull, which illustrates the paper by Mr. Marshall 'On the Brain of the
Chimpanzee' in the 'Natural History Review' for July, 1861. The sharper
definition of the lower edge of the cast of the cerebral chamber in the
Chimpanzee arises from the circumstance that the tentorium remained in
that skull and not in the Man's. The cast more accurately represents
the brain in Chimpanzee than in the Man; and the great backward
projection of the posterior lobes of the cerebrum of the former, beyond
the cerebellum, is conspicuous.

In many of these creatures, such as the Saimiri ('Chrysothrix'), the
cerebral lobes overlap and extend much further behind the cerebellum,
in proportion, than they do in man (Fig. 16)--and it is 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 mammals 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 compared with a similar cast of
the interior of a human skull, it will be obvious that the cast of the
cerebral chamber, representing 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. 20). 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 cerebellum of an extracted
and distorted brain for the natural relations of the parts; but his