99 
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, which, in the recent state, 
is interposed between the cerebrum and cerebellum, and 
prevents the former from pressing upon the latter, (see 
Fig. 17). 
This groove, therefore, indicates the line of separation 
between that part of the cranial cavity which contains the 
eerebrum, and that which contains the cerebellum; and as 
the brain exactly fills. the cavity of the skull, it is obvious 
that the relations of these two parts of the cranial cavity at 
once informs us of the relations of their contents. Now in 
man, in all the old world, and in all the new world Simie, 
with one exception, when the face is directed forwards, 
this line of attachment of the tentorium, or impression for the 
lateral sinus, as it is technically called, is nearly horizontal, 
and the cerebral chamber invariably overlaps or projects 
behind the cerebellar chamber. In the Howler Monkey or 
Mycetes (see Fig. 17), the line passes obliquely upwards and 
backwards, and the cerebral overlap is almost nil; while in 
the Lemurs, as in the lower mammals, the line is much more 
inclined in the same direction, and the cerebellar chamber 
projects considerably beyond the cerebral. 
When the gravest errors respecting points so easily settled 
as this question respecting the posterior lobes, can be authorita- 
tively propounded, it is no wonder that matters of observation, 
of no very complex character, but still requiring a certain 
amount of care, should have fared worse. Any one who 
cannot see the posterior lobe in an ape’s brain is not likely 
to give a very valuable opinion respecting the posterior cornu 
or the hippocampus minor. If a man cannot see a church, 
it is preposterous to take his opinion about its altar-piece or 
H 2 
