ON SOMATIC SEX-CHARACTERS 99 



parturition. In another specimen, twenty-one days 

 after heat, the milk glands were still more advanced, 

 with distended alveoli and enlarged ducts. The 

 alveoli contained a secretion which was almost 

 certainly milk. O'Donoghue states that the entire 

 series of growth changes in these animals up to 

 twenty-one days after heat is identical with that 

 which occurs in normally pregnant animals. 



O'Donoghue' s conclusion is in agreement with 

 that of Basch, 1 who states that implantation of the 

 ovaries from a pregnant bitch under the skin of the 

 back of a one-year-old bitch that was not pregnant 

 was followed by proliferation of the mammary 

 glands of the latter. After six weeks the glands 

 were considerably enlarged, and after eight weeks 

 they were caused to secrete milk by the injection of 

 extract of the placenta. It has to be remembered, 

 however, that the milk glands undergo considerable 

 growth, especially in the human species, at puberty 

 and at every menstruation, or at oestrus in animals, 

 which corresponds to menstruation. In these cases 

 there is no question of any influence of the foetus, and 

 experiment has shown that if the ovaries are removed 

 before puberty, neither the milk glands nor the uterus 

 undergo the normal development, and menstruation 

 does not occur. According to Marshall and Jolly 2 

 the symptoms of oestrus in castrated bitches were 

 found to result from the implantation of ovaries 

 from other individuals in the condition of oestrus. 



Before considering further the question of the 

 corpora lutea as organs of internal secretion, we may 

 briefly refer to the origin and structure of these 



1 Monatsschr. f. Kinderh. V., No. ix., Dec. 1909. 



2 Quart. Journ. Exp. Phys., i. and ii., 1908. 



