while the
other is deprived of the glands mentioned above) develop along
radically different lines. The stallion develops during his third year
into the noble animal described above. This third year is his period
of puberty and the changes which he undergoes physically and
psychically are closely parallel to the changes which the human
subject undergoes during his period of puberty. The gelding, on the
other hand, develops into an animal that is in every respect a neuter.
Physically this animal develops a body almost identical with that of
the female of the same species. Temperamentally the gelding is a
patient, plodding, beast of burden, and though under good grooming he
may show considerable life, while under the control of his driver, he
seldom shows any interest in other members of the horse family, either
male or female, and in the pasture or on the ranch his neutral sex
temperament is ever apparent. While he may contend mildly for a place
at the feeding trough, he never essays the defense of any weaker
members of the herd, and one stallion would put a hundred like him to
flight.

The thoughtful observer of this phenomenon cannot help wondering what
has made this radical difference in the development of these two
animals. The solution is not far to seek. From the beginning of
puberty to the beginning of senile decay, the stallion derives from
the testes what is referred to above as an internal secretion.

Physiologists have endeavored to determine exactly what substance
formed by the testes is reabsorbed into the lymph and blood. It may be
a substance called _spermin_, but whatever the substance is, the
physiologists agree that _the testes form some substance which is
absorbed by the blood and lymph, is carried to the brain and spinal
cord and there produces these profound effects indicated above_. So we
have discovered the source of the stallion's strength and beauty.

What is true of the horse is true of man. The young man at puberty
begins to receive from his testes the internal secretion which leads
to the development of his full manly powers. The sum total of the
qualities peculiar to manhood has been called VIRILITY. For want of a
better word, this term has been applied to the sum total of the male
qualities of any animal whatsoever, so that the male qualities of the
stallion are also compassed in the term virility.

The thoughtful and inquiring young man will naturally wish to know at
this point if this