direct determining influence in this direction, more
recently another view has been put forward, among others by Halban.[47]
According to this theory, the stimulus proceeding from the glands is
protective merely, not formative, nor directly stimulating the growth of
organs. In the fertilised ovum, it is supposed, the rudiment of sex
already exists, likewise the rudiment of the reproductive gland, and the
rudiments of the appropriate sexual characters. That is to say, the
development of the secondary sexual characters is not determined by the
presence of the reproductive gland; but the sex of the reproductive
gland and the associated sexual characters are already determined by
some common cause at the moment of fertilisation. But this theoretical
controversy has no very important bearing on the problem with which we
are especially concerned; and the influence of the reproductive gland
upon the development of the secondary sexual characters is admitted as
fully by Halban as it is by other writers, the only difference between
the two views lying in the dispute whether the influence of the glands
is of a formative or a protective nature. The influence exercised by the
reproductive glands on the development of the secondary sexual
characters can be adequately discussed, even though the precise way in
which that influence is exerted remains in dispute.

As to the general nature of the influence, two chief theories have to be
considered, viz., the nervous theory and the chemical theory. According
to the former, we must assume that a stimulus originates in the
reproductive glands, the testicles in the male, and the ovaries in the
female, and that these glands excite a kind of reflex action--that is,
that the stimulus passes to the central nervous system, and thence is
"reflected" to the periphery, where it promotes, either the growth of
particular parts of the body, _e.g._ the beard, or the development of
definite properties in certain organs, _e.g._ the characteristics of the
male larynx or of the female mamma. It is possible that the reflected
impulse stimulates trophic nerves. But it may be that in cases of early
castration the state of affairs is similar to that which obtains when
from earliest infancy one of the sense organs is wanting, as a result of
which the corresponding portions of the central nervous system are
found to undergo atrophy.[48] On this assumption, the manifest arrest of
the development of certain organs