5.24
The operation of reversion sometimes produces curious results.
Occasionally, under certain conditions, an individual of one sex will
assume many of the characters of the opposite sex, the reversion being to
its ancestors of this sex.
... not only structural peculiarities, but habits... and mental qualities,
such as courage, are among the characters which may be lost and gained in
this manner.
The influence of this form of reversion, which also occurs in the human
race, upon the production of insanity, is shown in two ways. In the first
place such changes are attended by, and are evidence of, an internal
revolution in the general organisation analogous to that which takes place
at puberty, when the secondary characters of sex are first assumed. The
inversion of sex cannot take place without a commotion analogous to that of
the assumption of sex ; and this change takes its place, therefore, among
the stresses which will hereafter be considered as determining causes of
insanity.
In the second place, this peculiar form of reversion is sometimes
accompanied by the production of long-lost characters peculiar to some
distant ancestral form. Such a reversion, if it take place in a man or
woman, and if it be to some cast of mind and habits peculiar to an ancestor
sufficiently remote, that is, to a form of life adapted to widely different
surroundings, may itself constitute insanity in the individual in whom it
appears.