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 question, it would indicate that the male secretory balance in man does not inhibit the female organs to the same extent that it apparently does in the Free-Martin cattle.  If established, the idea of “male dominance” in the human species would be undermined in a new place.  Such cases, if they occur at all, are exceedingly rare, but are of theoretical interest.  We must not rush to conclusions, as the earlier sociologists used to do.  Such a case would require careful analysis.  Its very uniqueness would suggest that it may not be due to the ordinary causes of hermaphroditism, but might arise from some obscure and unusual cause such as the fusion of two embryos at a very early stage.  The biochemistry involved is so intricate and so little understood that any deduction from the known facts would be purely speculative.]

Like the Free-Martin cattle, some accident has resulted in a mixture of male and female characteristics.  This accident occurs after a certain amount of embryonic development has taken place under the influence of the original predisposition of the fertilized egg.  The delicate secretory balance, so complex in man, is upset.  With partially developed organs of one type and with a blood-chemistry of the opposite one, some curious results follow, as the illustrative plates in Dr Bell’s book show.