m 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 (Figure 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 (Figure 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 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 comparable only to that
of one who should imagine that a man's lungs always occupy but a small
portion of the thoracic cavity--because they do so when the chest is
opened, and their elasticity is no longer neutralized by the pressure of
the air.

And the error is the less excusable, as it must become apparent to
every one who examines a section of the skull of any ape above a Lemur,
without taking the trouble to make a cast of it. For there is a
very marked groove in every such skull, as in the human skull--which
indicates the line of attachment of what is termed the 'tentorium'--a
sort of parchment-like shelf, or partition, whi