50 TABOO AND GENETICS 



the other. This blood-transfusion occurs in 

 nature in the " Free-Martin " cattle. (21.) 



Two embryos (twins) begin to develop in 

 separate membranes or chorions. At an early 

 stage in this development, however, the arteries 

 and veins of the two become connected, so that 

 the blood of each may circulate through the 

 body of the other. " If both are males or both 

 are females no harm results from this . . . ," 

 since the chemical balance which determines 

 the bodily form in each case is of the same type. 

 But if one is a male and the other a female, 

 the male secretory balance dominates the female 

 in a very peculiar fashion. The female repro- 

 ductive system is largely suppressed. She even 

 develops certain male organs, and her general 

 bodily appearance is so decidedly masculine 

 that until Dr Lillie worked out the case she 

 had always been supposed to be a non-functional 

 male. She is sterile. The blood transfusion 

 not only alters the sex-type of her body, but it 

 actually modifies the sex glands themselves, so 

 that the ovary resembles a testicle, though dis- 

 section proves the contrary. 



Why does not the female become a true, func- 

 tional 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 



