ISOLATION OF SEXUAL HORMONES 329 



of great interest to note that the uterus mascuhnus, which is 

 greatly developed in this species, showed marked thickening of 

 the muscle layers of the wall after injection of the above- 

 mentioned extracts. The muscle layers of the uterus masculinus 

 of the rabbit are considered by some authors as arising from the 

 Miillerian ducts. If this is really so, we have an example of an 

 organ homologous with the uterus (that is, an essentially female 

 organ) reacting to female sexual hormones in the male organism. 

 Stein and Herrmann (1921) have made similar statements 

 about male guinea pigs in which an hypertrophy of the mam- 

 mary glands also took place. But on account of certain dis- 

 crepancies in their individual experiments on rabbits they 

 think that farther confirmation is needed in regard to the 

 matter of the transformation of the uterus masculinus.^ 



Fellner (1921) has made the interesting statement that the 

 inhibitory action which female extracts have on the testicle, 

 may be obtained also by injecting Hpoid-containing extracts 

 of other organs, and even by injecting an extract from the 

 testicle itself. This testicular extract also promotes hyper- 

 trophy of the uterus and of the mammary gland. Fellner 

 concludes from his experiments that female sexual hormones 

 are present in the testicle though in a lesser quantity than in 

 various parts of the ovary. 



There is an interesting disparity between the results of 

 Herrmann and Fellner. Whereas Herrmann and Stein have 

 described, as already recorded, an inhibition of the develop- 

 ment of the vesiculae seminales and of the prostate gland in 

 rats, rabbits and guinea pigs, injected with an extract of the 

 corpus luteum, no such effects were observed by Fellner (1921, 

 pp. 200, 204). The latter author failed also to observe the 

 secretion from the hypertrophied mammary glands in injected 

 males as noted by Herrmann. I think that this absence of 

 agreement is to be explained by differences in the quantity 

 of the injected hormones. Where the injected quantity is 

 relatively small there will be a reaction only on the part of 

 the generative tissue of the testicle which is very sensitive; 

 where the injected quantities are greater there will be an 

 inhibition of other sex characters also. In Chapter IX. we shall 



1 According to Wertheimer and Dubois (see Ch. VIII., p. 338) the "uterus 

 masculinus" of the rabbit is nothing else than a seminal vesicle. Stein and 

 Herrmann were possibly mistaken when making all the above statements. 



