A Strain Male Mice Bearing Ovarian Grafts*

The early studies of Murray (11) suggested that male mice that had been castrated and trans planted with ovaries developed mammary cancer with approximately the same frequency as did virgin female mice of the same strain. Later, Loeb et al. (10), in a preliminary report in which no data were presented, stated that “aftertransplantation of ovaries into castrate male mice, the cancer rate and proliferative as well as secretory activities of the mammary gland were greater than after trans plantation of these organs into normal female mice.―With male mice of a hybrid cross, in which a high percentage of the virgin female mice devel op mammary cancer, it was observed in this labo ratory that castrate males bearing ovarian grafts developed mammary cancer with great frequence and at a significantly younger average age than did the virgin female mice of this particular cross (8).Thepresent investigation wasundertaken to study the rate and time of mammary carcinogene sis in male mice of a stock in which the virgin fe male mice have a low incidence of cancer, although breeding females have a high incidence.