ute tag--but larger in some
races than in others--which is the last dwindling relic of the third
eyelid, used in cleaning the front of the eye, which most mammals
possess in a large and well-developed form. It can be easily seen, for
instance, in ox and rabbit. In man and in monkeys it has become a
useless vestige, and the dwindling must be associated with the fact that
the upper eyelid is much more mobile in man and monkeys than in the
other mammals. The vestigial third eyelid in man is enough of itself to
prove his relationship with the mammals, but it is only one example out
of many. Some of these are discussed in the article dealing with the
human body, but we may mention the vestigial muscles going to the
ear-trumpet, man's dwindling counterpart of the skin-twitching muscle
which we see a horse use when he jerks a fly off his flanks, and the
short tail which in the seven-weeks-old human embryo is actually longer
than the leg. Without committing ourselves to a belief in the entire
uselessness of the vermiform appendix, which grows out as a blind alley
at the junction of the small intestine with the large, we are safe in
saying that it is a dwindling structure--the remains of a blind gut
which must have been capacious and useful in ancestral forms. In some
mammals, like the rabbit, the blind gut is the bulkiest structure in the
body, and bears the vermiform appendix at its far end. In man the
appendix alone is left, and it tells its tale. It is interesting to
notice that it is usually longer in the orang than in man, and that it
is very variable, as dwindling structures tend to be. One of the
unpleasant expressions of this variability is the liability to go wrong:
hence appendicitis. Now these vestigial structures are, as Darwin said,
like the unsounded, i.e. functionless, letters in words, such as the _o_
in "leopard," the _b_ in "doubt," the _g_ in "reign." They are of no
use, but they tell us something of the history of the words. So do man's
vestigial structures reveal his pedigree. They must have an historical
or evolutionary significance. No other interpretation is possible.

[Illustration: _Photo: New York Zoological Park._

CHIMPANZEE, SITTING

The head shows certain facial characteristics, e.g. the beetling eyebrow
ridges, which were marked in the Neanderthal race of men. Note the
shortening of the thumb and the enlargement of the big toe.]

[Illustration: _Photo: New York Zoological Park._

CHIMPANZEE,