Why does not the female become a true, functional male? Perhaps she does
in some cases. Such a one would not be investigated, since there would
be no visible peculiarity. In all the cases examined, the embryo had
begun its female development and specialization under the influence of
a predisposition of the female type in the fertilized egg, before the
transfusion began. There is no absolutely convincing mammalian evidence
of the complete upset of this predisposition, so all one can say is that
it is theoretically possible. Cases of partial reversal, sometimes
called "intersexes," are common enough. In birds and insects, where the
material is less expensive and experimentation simpler, males have been
produced from female-predisposed fertilized eggs and _vice versa_, as we
shall see in the next chapter.

Dr Bell[2, pp.133f.] points out that the so-called human "hermaphrodites"
are simply partial reversals of the sex type from that originally fixed
in the fertilized egg. As has been remarked earlier in these pages,
there is rarely if ever true hermaphroditism in higher animals--i.e.,
cases of _two functional sexes_ in the same individual. In fact, the
pathological cases in the human species called by that name are probably
not capable of reproduction at all.[A]

[Footnote A: _Note on human hermaphroditism_: This subject has been
treated in a considerable medical literature. See, for example, Alienist
and Neurologist for August, 1916, and New York Medical Journal for Oct.
23, 1915. It has been claimed that both human and higher mammalian
"hermaphrodites" have actually functioned for both sexes. Obviously,
absolute certainty about cause and effect in such cases, where human
beings are concerned, is next to impossible, because of lack of
scientific, laboratory control. If a case of complete functional
hermaphroditism in the human species could be established beyond