he human and simian types. Every
child comes into the world with a coat of rudimentary hair which is
shed at once. Aside from the growth of hair on the head, including the
brows and the lashes, the skin is quite free from any noticeable
growth of hair for months or even years. Beginning at the age of
puberty, however, the growth of hair is very much accelerated over the
whole pilous surface of the body, particularly upon the face, in the
axilla and over the pubic region. It is a generally recognized law of
biology, that, at the period of sexual development, the hairy
mammalian character becomes accentuated. The increase in the growth of
hair at this time can have only one interpretation, viz., that the
ancestors of man represented a very much higher degree of pilosity
than is the case with man at the present time. It is interesting to
note in this connection the almost universal attempt of men to rid the
face of this hairy growth by various devices, either pulling the beard
or shaving it. The origin of this custom of depilation probably dates
back to the remote past and has been observed as a custom among both
savages and civilized peoples.

b. =The Voice.=--In all animals the voice plays an important part in
sexual and social relations. In many animals the voice seems to have
almost no other function than as a sex call, or a communication
between mates and between parents and young. The human subject
illustrates this general biological principle in the profound changes
which the voice undergoes at the time of puberty. These changes in the
male subject consist in increasing the depth of the larynx, thereby
increasing the length of the vocal cords which in turn modifies the
pitch of the voice, usually about an octave, making it not only lower
but much more pleasing in quality and greatly increased in volume.

c. =Bone, Muscle and Gland.=--Of incalculably greater importance than
the changes described above though perhaps less noticeable to the
casual observer, are those physical changes which the body undergoes
during the first half of the period of adolescence. I refer to the
growth of bone, of muscles and of those internal organs associated
with nutrition.

The first step in these profound physical changes is a rapid growth in
height that makes itself manifest about the fifteenth year. It is not
at all unusual for a boy to grow from four to six inches in a year.
This increase in height is very largely due to a length