140 HEREDITY AND SEX 



The actual result conforms to the expectation. The 

 results of both of the experiments are consistent with 

 the view that one factor for horns in the male produces 

 horns, which we may attribute to the combined action 

 of the inherited factor and a secretion from the testes 

 which reenforces the action of the latter. This, how- 

 ever, should be tested by castrating the Fi males. In 

 the females, one factor for horns fails to produce horns, 

 while two factors for horns cause their development. 



Aside from some of the domesticated animals (horses, 

 cattle, dogs, cats, pigs), the only other mammals on 

 which critical experiments have been made — if we 

 exclude man — are the rat and the guinea pig. The 

 next case is unique in that the ovary was transplanted 

 to a male. 



Steinach removed the sex glands from the male 

 guinea pig and rat and transplanted into the same 

 animals the ovaries of the female, which established 

 themselves. Their presence brought about remarkable 

 effects on the castrated male. The mammary glands, 

 that are in a rudimentary condition in the male, be- 

 come greatly enlarged (Fig. 71). In the rat the hair 

 assumes the texture of that of the female. The skele- 

 ton is also more like that of the female than the male. 

 The size of the feminized rats and guinea pigs is less 

 than that of normal (or of castrated) males and 

 Hke that of the female (Fig. 72). Finally, in their 

 sexual behavior, the feminized rats were more like 

 females than like males. These cases are important 

 because they are the only ones in which success- 

 ful transplanting of the ovary into a male has been 

 accomplished in vertebrates. 



