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Note on the Resemblances and Differences in the Structure and the Development of the Brain in Man and Apes By: Thomas Henry Huxley (1825-1895) |
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BY PROFESSOR T. H. HUXLEY, F.R.S.
[This essay is taken from 'The Descent of Man and Selection in relation
to Sex' by Charles Darwin where it appears at the end of Chapter VII
which is also the end of Part I. Footnotes are numbered as they appear
in 'The Descent of Man.'] The controversy respecting the nature and the extent of the differences
in the structure of the brain in man and the apes, which arose some
fifteen years ago, has not yet come to an end, though the subject
matter of the dispute is, at present, totally different from what it
was formerly. It was originally asserted and re asserted, with
singular pertinacity, that the brain of all the apes, even the highest,
differs from that of man, in the absence of such conspicuous structures
as the posterior lobes of the cerebral hemispheres, with the posterior
cornu of the lateral ventricle and the hippocampus minor, contained in
those lobes, which are so obvious in man. But the truth that the three structures in question are as well
developed in apes' as in human brains, or even better; and that it is
characteristic of all the Primates (if we exclude the Lemurs) to have
these parts well developed, stands at present on as secure a basis as
any proposition in comparative anatomy. Moreover, it is admitted by
every one of the long series of anatomists who, of late years, have
paid special attention to the arrangement of the complicated sulci and
gyri which appear upon the surface of the cerebral hemispheres in man
and the higher apes, that they are disposed after the very same pattern
in him, as in them. Every principal gyrus and sulcus of a chimpanzee's
brain is clearly represented in that of a man, so that the terminology
which applies to the one answers for the other. On this point there is
no difference of opinion. Some years since, Professor Bischoff
published a memoir (70. 'Die Grosshirn Windungen des Menschen;'
'Abhandlungen der K. Bayerischen Akademie,' B. x. 1868.) on the
cerebral convolutions of man and apes; and as the purpose of my learned
colleague was certainly not to diminish the value of the differences
between apes and men in this respect, I am glad to make a citation from
him. "That the apes, and especially the orang, chimpanzee and gorilla, come
very close to man in their organisation, much nearer than to any other
animal, is a well known fact, disputed by nobody. Looking at the matter
from the point of view of organisation alone, no one probably would
ever have disputed the view of Linnaeus, that man should be placed,
merely as a peculiar species, at the head of the mammalia and of those
apes. Both shew, in all their organs, so close an affinity, that the
most exact anatomical investigation is needed in order to demonstrate
those differences which really exist. So it is with the brains. The
brains of man, the orang, the chimpanzee, the gorilla, in spite of all
the important differences which they present, come very close to one
another" (loc. cit. p. 101). There remains, then, no dispute as to the resemblance in fundamental
characters, between the ape's brain and man's: nor any as to the
wonderfully close similarity between the chimpanzee, orang and man, in
even the details of the arrangement of the gyri and sulci of the
cerebral hemispheres. Nor, turning to the differences between the
brains of the highest apes and that of man, is there any serious
question as to the nature and extent of these differences. It is
admitted that the man's cerebral hemispheres are absolutely and
relatively larger than those of the orang and chimpanzee; that his
frontal lobes are less excavated by the upward protrusion of the roof
of the orbits; that his gyri and sulci are, as a rule, less
symmetrically disposed, and present a greater number of secondary
plications. And it is admitted that, as a rule, in man, the
temporo occipital or "external perpendicular" fissure, which is usually
so strongly marked a feature of the ape's brain is but faintly marked... Continue reading book >>
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