568 SWALE VINCENT 



1908 observed that injection of extract of fetal calf caused some mam- 

 mary growth in rabbits. It is therefore concluded that the effects de- 

 scribed by Lane-Claypon and Starling are not specific for a single kind 

 of animal. Hieape points out that it is well known that virgin animals 

 sometimes produce milk. Hence, it seems clear that the beginning of 

 the development of the gland dates from some point of time prior to 

 or during pro-estrum or estrus, and occurs normally quite apart from 

 pregnancy, and that since the full functional development of the gland 

 may be experienced by virgin animals, this must occur without any 

 stimulus from a fetus. Heape believes that the source of the stimulus 

 which excites the development of the mammary gland is to be found in 

 what he calls "gonadin," secreted by the ovary at that time, if not in the 

 "generative ferment'' which, he holds, governs the activity of the genera- 

 tive glands. The theory of Lane-Claypon and Starling was also criti- 

 cized by Frank and linger, who definitely suggested that it is the per- 

 sistent corpus luteum of pregnancy which produces mammary growth. 

 O'Donoghue points out that in Dasyurus the life of the corpus luteum 

 in the pregnant and non-pregnant animals can be divided into three 

 stages: (1) period of formation, (2) period of growth, (3) period of 

 constancy. The formative growth of the mammary gland also falls into 

 three divisions: (1) commencement of growth, (2) period of active 

 growth, (3) period of constancy. These three periods in the corpus 

 luteum precede by a short time the corresponding periods in the mam- 

 mary glands in such a manner as to suggest cause and effect. Lane- 

 Claypon and Starling found that removal of the ovaries (containing 

 corpora lutea) is followed by cessation of growth and regression of the 

 mammary gland. As we have seen above (p. 565), O'Donoghue observed 

 that, if follicular rupture is not followed by formation of corpora lutea, 

 there is no growth of the mammary glands. The conclusion seems un- 

 avoidable that the hormone causing the growth of the mammary glands 

 during pregnancy and at other times is produced in the corpora lutea. 



The "Interstitial Gland" of the Ovary 



The "interstitial cells" or the "interstitial gland" have occupied a 

 prominent place in all discussions of ovarian function during the last 

 fifteen or twenty years. It is especially in regard to proved or suspected 

 internal secretion on the part of the female gonad that these structures 

 have received so much attention. The true significance of the cells in 

 question is not known, and much of the confusion at present existing in 

 the literature arises from the fact that the majority of workers on the 

 subject have restricted their inquiries to a narrow field of investigation, 

 while more general considerations have escaped their notice. 



