directions toward the bent elbow. This is so useless in man that it can
be explained only as a survival.

There are some other survivals in man of ancient structures to which a
passing allusion must suffice. In man's eye is a minute membrane, the
semilunar fold, which is absolutely useless in his economy. There is
every reason to believe that this is the rudiment of a membrane which is
fully developed in many animals, and is especially useful to birds, the
nictitating membrane, or third eyelid. Again, the muscles which move the
skin in many animals, especially in horses, have left inactive remnants
in many parts of the human body. These are normally active only in the
forehead, where they serve to lift the eyebrows, but they occasionally
become active elsewhere. Thus there are some persons who can move the
skin of the scalp. Darwin cites some who could throw heavy books from
the head in this manner. The same may be said of the rudimentary muscles
of the ear. There are persons who can move their ears in the same way as
is done by the lower animals. Again, the whole external ear may be
looked upon as a rudimentary structure, since it does not appear to aid
the hearing in man. As regards the pointed ear of man's probable
ancestor, Darwin calls attention to what seems a trace in man of the
lost tip.

Carrying this consideration farther, it may be asked, Of what use are
the five toes to man? Would not a solid foot have answered the purpose
of walking quite as well? But as survivals their presence is fully
accounted for, since they are indispensable to many of the lower
animals. Question may also be made of the utility of the large number of
bones in the wrist and heel of man. Equal flexibility of the joint could
certainly have been obtained with a smaller number of bones. It is only
when these are traced back to their probable origin in the walking
organs of the fish ancestor of the batrachians that their presence
becomes explainable. They are apparently survivals of a very ancient
structure, originated for swimming, 