Wm. R. Lyons ^ig 



mized rats. Nathanson and co-workers," by giving hypophyscctoniizcd rats 

 estradiol benzoate plus a "growth complex" containing growth, lactogenic, 

 and adrenotrophic hormones, were able to maintain the mammary glands in 

 eight of twenty-four animals. Reece and Leonard"' obtained mammary-duct 

 growth in hypophysectomized rats injected with estrin plus a "growth" prepa- 

 ration which apparently was a inixture of anterior-lobe hormones. They claim 

 that slight growth was produced in such animals by injecting the "growth" 

 preparation alone, and because of this annoimced an alternative hypothesis to 

 that of Turner and co-workers, namely that "either estrogen facilitated the 

 mammogenic effect of the growth hormone or that growth hormone facilitated 

 and was responsible for the effect of estrogen." As quoted by Petersen^" "Sam- 

 uels et al. using a more highly purified growth hormone corroborate the 

 findings of Reece and Leonard, but contend other pituitary hormones are 

 also needed." Gardner and White"' by giving estrone plus pure prolactin 

 induced mammary growth in hypophysectomized mice comparable to that 

 previously reported in hypophysectomized mice injected with estradiol dipro- 

 pionate and progesterone;"' apparently no lobulo-alveolar growth was in- 

 duced in these investigations. Gardner and White suggest "that prolactin may 

 either sensitize the mammary tissue of hypophysectomized mice to estrogen 

 or improve the general condition of these animals so that mammary pro- 

 liferation may occur." 



The literature cited has to do for the most part with the roles played by 

 the ovary and the pituitary in duct and alveolar development of the mammary 

 gland, since in the report to follow only that type of mammary growth (pro- 

 lactational) and not functional (or lactational) growth is considered. The 

 latter deserves separate treatment and seems to require a different set of syn- 

 ergizing hormones. It is difficult to agree with Uyldert, David and Freud"^ 

 that "a study of the literature with reference to the problem of the mammary 

 gland and lactation gives one the impression that there is no endocrinological 

 pioblem to mammary evolution left unsolved." However, these authors ad- 

 mirably sum up the true situation when they write that "various parts of these 

 [developmental] processes can be artificially reproduced with the aid of hor- 

 mones, btit the whole complex eludes attempts to induce it artificially." Prog- 

 ress will have been made when we learn what combination of purified hor- 

 mones simultaneously maintains pregnancy and causes nonlactating lobulo- 

 alveolar mammary growth, and what combination subsequently maintains a 

 mammary apparatus adequate in every respect for the suckling of the offspring. 

 In 1938 it was shown"" that postpartum lactation could be induced and main- 

 tained in hypophysectomized rats by injecting extremely high doses of a lacto- 

 genic-adrenotrophic hormone combination, but the mothers seemed unable 

 to eject their milk, possibly due to a posterior-pituitary deficiency. More re- 

 cently, because of the availability of purified hormones, it has seemed advisable 

 to return to a study of the hormonal factors necessary for prolactational or 

 lobulo-alveolar growth. During the past year with the constant help and advice 



