Dr Blair Bell[14,15] has collected a mass of evidence on intersexes in the human species.  This includes his own surgical and other cases, as well as many treated by his colleagues, and a very considerable review of the medical literature.  He not only believes in degrees of femininity in women, but has worked out classifications which he claims to have found of great practical value in surgery.[14, pp.166-7] As noted above, Riddle discovered that his more feminine female pigeons were often killed by a dose of testicular extract which was practically harmless to a partially masculinized female.  Sex in the human species being a matter of all the glands organized into a complex, the quantitative “strength” of that complex would be useful to know before removing any one secretion from it.  Dr Bell states that the ooephorectomy operation (removal of ovaries) may be performed upon a masculine type of woman with “little disturbance of the metabolism...”  But he thinks that the degree of masculinity should always be carefully observed before undertaking such operations, which in some cases have most undesirable effects.

At one end of the scale, this surgeon places the typically feminine woman in all her characteristics—­with well-formed breasts, menstruating freely and feminine in instincts—­he says “mind.”  The intermediate grades consist, he says, of women whose metabolism leans toward the masculine type.  Some have sexual desires but no maternal impulse.  Others desire maternity but take no interest in sex activity, or positively shun it.  The physical manifestations of masculine glandular activity take the form of pitch of voice, skin texture, shape and weight of bones, etc.  Some of the inter-grades are a little hard to define—­the human species is such an inextricable mixture of races, etc.; but Dr Bell does not hesitate to describe the characteristically masculine woman of the extreme type, who “shuns both sexual relations and maternity...(She) is on the fringe of femininity.  These women are usually flat-breasted and plain.  Even though they menstruate, their metabolism is often for the most part masculine in character:  indications of this are seen in the bones which are heavy, in the skin which is coarse, and in the aggressive character of the mind...If a woman have well-developed genitalia, and secondary characteristics, she usually is normal in her instincts.  A feebly menstruating woman with flat breasts and coarse skin cannot be expected to have strong reproductive instincts, since she is largely masculine in type...”

The glandular and quantitative explanation of sex, instead of being abstruse and complicated, brings the subject in line with the known facts about inheritance generally.  The dual basis for femaleness and maleness in each individual simply means that both factors are present, but that only one expresses itself fully.  The presence of such a dual basis is proved by the fact that in castration and transplantation experiments both are exhibited by the same individual in a single lifetime.  In the case of the Free-Martin cattle, even the female sex-glands are modified toward the male type to such an extent that they were long mistaken for testes.  The same applies to some glands found in human “hermaphrodites,” as Dr Bell’s plates show.