Departments of Physiology, Anatomy, and Obstetrics and Gynecology, Louisiana State University Medical Center, New Orleans, Louisiana 70112, U.S.A.
Lipschütz (1927) suggested that the number of eggs shed by an animal is not determined by the number of ova present, but by some extra-ovarian factor. When Breward & Zuckerman (1949) attempted to test this hypothesis, they showed that multiple ovarian grafts in randomly bred female rats caused a decrease in follicular development and the weight of the ovaries in situ. These findings were later attributed to immunological rather than endocrinological factors (Mandl & Zuckerman, 1951). In the present study, the influence of `extra' ovarian tissue on the number of eggs ovulated and follicular development was re-investigated using highly inbred Fischer 344 rats. In such strains skin homografts are permanently accepted, verifying the isohistogenicity of the strain (Warren, Lofgreen & Steinmuller, 1973). Since skin grafts are more difficult to transplant permanently in