A character which is thus variable within the limits of a single
group can have no great taxonomic value.
It is further established, that the degree of asymmetry of the
convolution of the two sides in the human brain is subject to
much individual variation; and that, in those individuals of the
Bushman race who have been examined, the gyri and sulci of the
two hemispheres are considerably less complicated and more
symmetrical than in the European brain, while, in some
individuals of the chimpanzee, their complexity and asymmetry
become notable. This is particularly the case in the brain of a
young male chimpanzee figured by M. Broca. ('L'ordre des
Primates,' p. 165, fig. 11.)
Again, as respects the question of absolute size, it is
established that the difference between the largest and the
smallest healthy human brain is greater than the difference
between the smallest healthy human brain and the largest
chimpanzee's or orang's brain.
Moreover, there is one circumstance in which the orang's and
chimpanzee's brains resemble man's, but in which they differ from
the lower apes, and that is the presence of two corpora
candicantia--the Cynomorpha having but one.
In view of these facts I do not hesitate in this year 1874, to
repeat and insist upon the proposition which I enunciated in
1863: (74. 'Man's Place in Nature,' p.
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