28 INTERNAL SECRETIONS 



layers. Glands are absent in the mucosa and the epithelium 

 is flattened. The muscle layers are several times thinner 

 than in a normal uterus. The vascularization of the uterus 

 is also diminished. Similar observations have been made on 

 guinea pigs, on rats, and on the cow. Athias (1919) has shown 

 in experiments on the isolated uterus of guinea pigs that the 

 uterus after castration is functionally different from the normal 

 one; the intensity of the spontaneous contractions of the 

 uterus decreases after castration or they ma}' even disappear. 



What is stated about the features of the mammary glands 

 of animals after castration is just as contradictory as in the 

 case of man. Sellheim (1901) described in calves castrated at 

 six or eight weeks of age an augmented growth of the mammary 

 glands, both nipple and glandular tissue. The older the ox is 

 the more striking is the difference between it and the bull, the 

 nipples of the ox being longer and broader, the glandular tissue 

 showing microscopically a richer development in the ox than 

 in the bull. Even milk secretion after castration is reported. 

 In male guinea pigs and rabbits prepuberally castrated, I 

 never could observe an increased growth of the nipples; but 

 the question is worth further investigation in regard to the 

 microscopical character of the glandular tissue. Very con- 

 tradictory, also, are the statements made on the mammary 

 gland after castration in the female mammal. Halban and 

 Steinach found that the mammary gland of prepuberally 

 castrated guinea pigs remained undeveloped. But some 

 authors seem to have observed that after postpuberal castra- 

 tion the mammary gland not only persists, but can even increase 

 and secrete colostrum (Kammerer, 1912, pp. 108 and 109). I 

 think that a mistake may have occurred here, as small particles 

 of ovarian tissue left unintentionally in the body can replace 

 functionally the whole ovary, and they can grow and even 

 undergo a very marked hypertrophy, as w^as stated by Car- 

 michael and Marshall (1908) and confirmed by myself (1922). 



In prepuberally castrated animals heat never occurs; the 

 genital organs not being fully developed cannot undergo 

 the characteristic cychcal changes. With postpuberally 

 castrated animals the data are contradictory, as they are with 

 those on menstruation in women. But in general it seems 

 that investigators have not directed their attention in a suffi- 

 cient manner to this question in mammals. Marshall affirmed 



