The functioning of the axis hypophysis-ovary was studied in rats which had received an injection of 100 .mu.g estradiol benzoate in the 1st days of life. The experimental method was the parabiosis of 2 animals (male or female, normal or estrogenized, intact or spayed) in different combinations. Estrogenization apparently damages the hypopysis as well as the ovary to such a degree that both glands cease to function normally. Injected gonadotropins can produce luteinization of estrogenized ovaries. This effect appears only as a direct consequence of hormone administration. Exogenous gonadotropins can never trigger cyclical function of estrogenized ovaries.