-teeth are usually furnished with three
separate fangs, and are usually sound [i. e. not specially liable
to decay]; they also differ from the other molars in size, less
than in the Caucasian races.

Now, in addition to these there are other respects in which the
dwindling condition of wisdom-teeth is manifested--particularly with
regard to the pattern of their crowns. Indeed, in this respect it would
seem that even in the anthropoid apes there is the beginning of a
tendency to degeneration of the molar teeth from behind forwards. For if
we compare the three molars in the lower jaw of the gorilla, orang, and
chimpanzee, we find that the gorilla has five well-marked cusps on all
three of them; but that in the orang the cusps are not so pronounced,
while in the chimpanzee there are only four of them on the third molar.
Now in man it is only the first of these three teeth which normally
presents five cusps, both the others presenting only four. So that,
comparing all these genera together, it appears that the number of
cusps is being reduced from behind forwards; the chimpanzee having lost
one of them from the third molar, while man has not only lost this, but
also one from the second molar,--and, it may be added, likewise
partially (or even totally) from the first molar, as a frequent
variation among civilized races. But, on the other hand, variations are
often met with in the opposite direction, where the second or the third
molar of man presents five cusps--in the one case following the
chimpanzee, in the other the gorilla. These latter variations,
therefore, may fairly be regarded as reversionary. For these facts I am
indebted to the kindness of Mr. C. S. Tomes.

[Illustration: FIG. 24.--Molar teeth of lower jaw in Gorilla, Orang,
and Man. Drawn from nature, nat. size (_R. Mus. Coll. Surg._).]

(10) _Perforations of the humerus._--The peculiarities which we have to
notice under this heading are two in number. First, the supra condyloid
foramen is a normal feature in some of the lower Quadrumana (Fig. 25),
where it gives passage to the great nerve of the fore-arm, and often
also to the great artery. In man, however, it is not a normal feature.
Yet it occurs in a small percentage of cases--viz., according to Sir W.
Turner, in about one per cent., and therefore is regarded by Darwin as a
vestigial character. Secondly, there is inter-condyloid foramen, which
is also situated near the lower end of t