which results from castration is to be
regarded as the sequel of a partial atrophy of certain portions of the
brain. Of late, however, the chemical theory, that the results of
castration are dependent on the lack of the internal secretion of the
excised glands, has gained ground at the expense of the nervous theory.
The reason for this change of view is that much which was unsuspected in
former years has recently been learned about the chemical activities of
other glands. It suffices to allude to the function of the thyroid body.
According to this chemical theory, chemical substances are prepared in
the reproductive glands, and these substances exert a specific influence
in promoting the development of the secondary sexual characters. The
same theory has been invoked to account for the alleged ill effects of
sexual abstinence, it being suggested that the reabsorption of glandular
products properly destined for excretion may give rise to toxic
effects.[49] If it be assumed that the testicles can secrete substances
upon the influence of which the development of the secondary sexual
characters depends, it is obvious that these substances have nothing to
do with the spermatozoa, inasmuch as the testicles exert the influence
under consideration at an age at which the formation of spermatozoa has
not yet begun. The substances that act in this way must be of a
different kind. As was pointed out earlier in this book (p. 19), recent
researches have shown that the testicles possess a twofold activity; and
some French physicians even go so far as to say that the testicle is not
a single gland, but two glands. They distinguish between the gland that
prepares the spermatozoa and the interstitial gland.[50] Whilst the
formation of spermatozoa subserves the generative act, the function of
the interstitial gland is to prepare substances which pass into the
lymph or blood-stream, and give rise to the development of the secondary
sexual characters. Thus, the effects of castration are due, on this
theory, not to the absence of the formation of spermatozoa, but to the
absence of the products of the interstitial glands. French investigators
consider that the assumption that such an interstitial gland exists is
justified by the results of experimental work.

Whichever theory we accept, the chemical or the nervous, both theories
harmonise equally with the fact that in boys, before the formation of
spermatozoa begins, processes occur in the tes