Uterine distension and the function of the corpora lutea in the guinea-pig.

1. The presence of two glass beads (7 x 3 mm) in each horn of the uterus was associated with a reduction of 3-4 days in the length of the oestrous cycle.2. Two beads inserted into each uterine horn between days 2 and 4 exerted a greater effect on the oestrous cycle than either one bead in each horn or four beads in one horn only. Two beads located in one horn failed to affect cycle length.3. Measurement of the volume of the corpora lutea showed that distension of the uterus induced a premature regression in the size of the luteal bodies.4. When glass beads were present in one uterine horn, early and unilateral regression of the corpora lutea in the ovary adjacent to the distended horn was observed. Regression of the corpora lutea in the opposite ovary proceeded normally.5. In view of the local effect of uterine distension and other information, it is concluded that each uterine horn can produce a luteolytic substance which is conveyed to the neighbouring ovary to act upon the corpora lutea.