But this is not all. The supposed fact that female secondary characters in
Vertebrates are absent in the male is completely disproved for Mammals by
the presence of rudimentary mammary glands in the male. It is true that
secondary sex-characters are usually positive in the male, while those of
the female are apparently negative, but in the case of the mammary glands
the opposite is the case. There is no room for doubt that the mammary
glands are an essentially female somatic sex-character, not only in their
function but in the relation between the periodicity of that function and
those of the ovaries and uterus, and it is equally certain from their
presence in rudimentary condition in the male that they are not absent
from the male constitution.

INFLUENCE OF GONADS DUE TO HORMONES

The existence and the influence of hormones or internal secretions may be
said to have been first proved in the case of the testes, for Professor A.
A. Berthold [Footnote: 'Transplantation der Hoden,' _Archiv. f Anat. u.
Phys._, 1849.] of Goettingen in 1849 was the first to make the experiment
of removing the testicles from cocks and grafting them in another part of
the body, and finding that the animals remained male in regard to voice,
reproductive instinct, fighting spirit, and growth of comb and wattles. He
also drew the conclusion that the results were due to the effect of the
testicle upon the blood, and through the blood upon the organism. Little
attention was paid to Berthold's experiment at the time. The credit of
having been the first to formulate the doctrine of internal secretion is
generally given to Claude Bernard. He discovered the glycogenic function
of the liver, and proved that in addition to secreting bile, that organ
stores up glycogen from the sugar absorbed in the stomach and intestines,
and gives it out again as sugar to the blood. In 1855 he maintained that
every organ of the body by a process of internal secretion gives up