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So far as cerebral structure goes, therefore, it is clear that 
Man differs less from the Chimpanzee or the Orang, than 
these do even from the Monkeys, and that the difference 
between the brains of the Chimpanzee and of Man is almost 
insignificant, when compared with that between the Chim- 
panzee brain and that of a Lemur. 
It must not be overlooked, however, that there is a very 
striking difference in absolute mass and weight between the 
lowest human brain and that of the highest ape —a difference 
which is all the more remarkable when we recollect that a 
full grown Gorilla is probably pretty nearly twice as heavy as 
a Bosjes man, or as many an European woman. It may be 
doubted whether a healthy human adult brain ever weighed 
less than thirty-one or -two ounces, or that the heaviest Gorilla 
brain has exceeded twenty ounces. 
This is a very noteworthy circumstance, and doubtless will 
one day help to furnish an explanation of the great gulf which 
intervenes between the lowest man and the highest ape in 
intellectual power ;* but it has little systematic value, for the 
* Tsay help to furnish: for I by no means believe that it was any original 
difference of cerebral quality, or quantity, which caused that divergence between 
the human and the pithecoid stirpes, which has ended in the present enormous 
gulf between them. It is no doubt perfectly true, in a certain sense, that all 
difference of function is a result of difference of structure; or, in other words, 
of difference in the combination of the primary molecular forces of living sub- 
stance; and, starting from this undeniable axiom, objectors occasionally, and 
with much seeming plausibility, argue that the vast intellectual chasm between 
the Ape and Man implies’a corresponding structural chasm in the organs of the 
intellectual functions ; so that, it is said, the non-discovery of such vast differ- 
ences proves, not that they are absent, but that Science is incompetent to detect 
them. A very little consideration, however, will, I think, show the fallacy of 
this reasoning. Its validity hangs upon the assumption, that intellectual power 
depends altogether on the brain—whereas the brain is only one condition out 
of many on which intellectual manifestations depend ; the others being, chiefly, 
the organs of the senses and the motor apparatuses, especially those which are 
concerned in prehension and in the production of articulate speech. 
A man born dumb, notwithstanding his great cerebral mass and his inheritance 
of strong intellectual instincts, would be capable of few higher intellectual 
manifestations than an Orang or a Chimpanzee, if he were confined to the society 
