Ovulation in the guinea-pig. I. The ruptured follicle.

Guinea-pig ovarian follicles were studied by light and electron microscopy. All freshly ruptured follicles showed small blood vessels within the stratum granulosum as well as amongst the cells of the theca interna. The evidence suggests that the marked increase in the size of the preovulatory follicle stretches the basement membrane between theca interna and stratum granulosum to breaking point at several places and the resultant passage of blood from the theca interna into the stratum granulosum flushes out the oocyte.