Abstract
Crystalline estradiol or stilbestrol was applied to one ovary of the immature rat leaving the other ovary untreated. The estrogen treated ovary exhibited several unilaterally differential responses: (1) a greater increase in weight, (2) formation of corpora lutea, (3) an increased responsiveness to endogenous and exogenous gonadotrophins. In control experiments crystalline testosterone or progesterone was applied to one ovary with, or without, estradiol being placed on the other ovary. These experiments demonstrate that estrogen has a local stimulatory effect within the ovary as well as a systemic effect via the pituitary.