The cyclic changes in the mammary gland of the guinea pig

Abstract

Our interest in the character of the cyclic changes of the mammary gland and in their mechanism was twofold, (1) In former investigations Loeb has shown that an early extirpation of the ovaries reduces to a very marked extent the incidence of cancer of the breast in mice. It was therefore of interest to inquire more closely into the relations between ovaries and mammary gland, and (2) we wished to determine whether there exists a parallelism between the cyclic changes in the mammary gland on the one hand and in the ovaries and uterus on the other hand. One of us had formerly shown that in the cyclic changes of ovaries and uterus we could distinguish two phases: the first, comprising ovulation and the heat changes in the uterus, depends upon the absence of the corpus luteum. These are prevented by a substance secreted by the lutein cells. This phase is, however, dependent upon another constituent of the ovaries. The second phase, comprising the further cyclic changes in the uterus as well as the production of decidua and deciduomata, requires a substance secreted by the corpus luteum. Do corresponding phases exist in the case of the mammary gland?

Relatively little is known concerning the cyclic changes in the mammary gland. Bouin and Ancel, as well as Frank and Unger, have shown that in the rabbit, even in the absence of pregnancy, but in the presence of corpora lutea, proliferation takes place in the mammary gland. Proliferation also occurs regularly during pregnancy. Frank and Unger have furthermore demonstrated that the experiments of Starling and others concerning the source of the growth substance which acts on the mammary gland are not conclusive.

Our investigations concern the cyclic changes in the mammary gland of the guinea pig.