tion as
the only function of the testicle. But it is now firmly established that
these glands exercise influence in other ways. We know that bodily and
mental development are affected by the removal of the testicles; and
that the influence is greater the earlier in life the castration takes
place. A number of secondary sexual characters remain undeveloped. The
beard does not grow; in many instances a thick _panniculus adiposus_ is
formed; there are changes in the growth of the bones; the voice remains
a soprano; and the other reproductive organs are imperfectly developed,
the penis and the prostate remaining comparatively small An early
castration does not, of course, result in the obliteration of all
differences between the male and the female; we must rather say that a
part only of the typical differential characters of sex remain
undeveloped. The earlier assumption, that the secretion of semen
competent to effect fertilisation influenced the development of the
secondary sexual characters, has of late been more and more generally
abandoned. Many considerations tell against such a theory, more
especially a comparison of the three following facts. First, if
castration is not effected until after the formation of spermatozoa has
already begun, the familiar results of this operation are either
entirely wanting, or else appear to a small extent only, and are limited
to a small number of the secondary sexual characters. Secondly, the
results of castration are most marked when the operation is performed in
early childhood. Thirdly, when castration is effected in the later years
of childhood, but before the secretion of fertilising semen has taken
place, the results are intermediate in degree, being much less marked
than in the second class of cases, but more extensive than in the first.
If the secretion of a fertilising semen were the principal factor in the
development of the secondary sexual characters, we should expect the
results of castration to be the same whether the operation were
performed early in childhood or late so long as it was done before any
spermatozoa had been formed.

The secondary sexual characters are, therefore, independent of the
formation of spermatozoa, and the appearance of these characters must
depend upon other processes, occurring much earlier in life. Thus, in
persons who were castrated in the eighth or ninth year of life, we note
the presence of definite secondary sexual characters, which are,