he humerus, but more in the
middle of the bone. This occurs, but not constantly, in apes, and also
in the human species. From the fact that it does so much more frequently
in the bones of ancient--and also of some savage--races of mankind (viz.
in 20 to 30 per cent. of cases), Darwin is disposed to regard it also as
a vestigial feature. On the other hand, Prof. Flower tells me that in
his opinion it is but an expression of impoverished nutrition during
the growth of the bone.

[Illustration: FIG. 25.--Perforation of the humerus (supra-condyloid
foramen) in three species of Quadrumana where it normally occurs,
and in Man, where it does not normally occur. Drawn from nature (_R.
Coll. Surg. Mus._).]

(11) _Flattening of tibia._--In some very ancient human skeletons, there
has also been found a lateral flattening of the tibia, which rarely
occurs in any existing human beings, but which appears to have been
usual among the earliest races of mankind hitherto discovered. According
to Broca, the measurements of these fossil human tibiae resemble those of
apes. Moreover, the bone is bent and strongly convex forwards, while its
angles are so rounded as to present the nearly oval section seen in
apes. It is in association with these ape-like human tibiae that
perforated humeri of man are found in greatest abundance.

On the other hand, however, there is reason to doubt whether this form
of tibia in man is really a survival from his quadrumanous ancestry.
For, as Boyd-Dawkins and Hartmann have pointed out, the degree of
flattening presented by some of these ancient human bones is _greater_
than that which occurs in any existing species of anthropoid ape. Of
course the possibility remains that the unknown species of ape from
which man descended may have had its tibia more flattened than is now
observable in any of the existing species. Nevertheless, as some doubt
attaches to this particular case, I do not press it--and, indeed, only
mention it at all in order that the doubt may be expressed.

Similarly, I will conclude by remarking that several other instances of
the survival of vestigial structures in man have been alleged, which are
of a still more doubtful character. Of such, for example, are the
supposed absence of the genial tubercle in the case of a very ancient
jaw-bone of man, and the disposition of valves in human veins. From the
former it was argued that the possessor of this very ancient jaw-bone
was