616 THE PHYSIOLOGY OF REPRODUCTION 



it is not impossible that substances ma} 7 diffuse outward from tbe 

 embryo and be absorbed by the uterine mucous membrane, and so be 

 carried into the maternal circulation. 



Miss Lane-Claypon and Starling, however, never contended that 

 the foetus is the sole source of the stimulus for mammary develop- 

 ment. On the other hand, they specially mentioned that the growth 

 of the mammary glands which occurs at puberty, for instance, can 

 only be attributed to ovarian influence, since it does not take place 

 if the ovaries have been previously removed. It is not improbable, 

 therefore, that an ovarian stimulus is also responsible for producing 

 the growth of the glands in Monotremes, in just the same kind of 

 way as has been demonstrated for other animals. 



The foetal hormone theory has now been superseded by the 

 hypothesis of the corpus luteum as the main controlling factor in 

 the growth of the mammary glands. Starling and Lane-Claypon, 

 however, did useful service in emphasising the part played by the 

 foetus in promoting the growth of the glands in pregnancy, for it is 

 only in the presence of the foetus in utero, at any rate in placental 

 Mammals, that the complete development of the glands followed by 

 full lactation is normally attained. 



The Corpus Luteum. Ancel and Bourn 1 were the first to show 

 that the growth of the mammary glands during the first part of 

 pregnancy is due to the corpus luteum. Their researches were upon 

 the rabbit which only ovulates after copulation (see p. 129), so that 

 normally, since the discharged ova are fertilised, the presence of 

 corpora lutea is always associated with pregnancy. Ancel and Bouin, 

 however, by employing males in which the vasa deferentia had been 

 severed, were able to induce the formation of corpora lutea without 

 the occurrence of gestation. The same results can be brought about 

 by severing the Fallopian tubes of the female or by removing the 

 uterus, as was shown later by the present writer, working in 

 conjunction with Mr. Hammond. 2 We described the condition 

 produced as one of "pseudo-pregnancy," a name already used by 

 Hill and O'Donoghue 3 to designate the similar state of functional 

 correlation which occurs normally in the Marsupial cat (Dasyurus 

 vivemnm) after spontaneous ovulation. These authors have shown 

 that in Dasyurus the changes undergone by the mammary glands 

 are identical whether pregnancy supervenes or not (see p. 36). 



1 Ancel and Bouin, see references, p. 371. For a full account of the changes 

 in the glands with many references to literature see Schil, Recherche* sur la 

 Cllande Mammaire, Nancy, 1912. 



2 Hammond and Marshall, "The Functional Correlation between the 

 Ovaries, Uterus, and Mammary Glands in the Rabbit," Prof!. Roy. Soc., B., 

 vol. Ixxxvii., 1914. 



3 Hill and O'Donoghue, "The Reproductive Cycle in the Marsupial Cat, 

 Dasyurus viverrinm" Quar. Jour. Micr. Sci-ence, vol. lix., 1913. 



