Discovery reports (1962) Discovery reports discoveryreports31inst Year: 1962 360 DISCOVERY REPORTS of pregnancy which was 19 cm. in diameter lacked a cavity. Conversely, cavities are found in the much smaller corpora lutea of other animals; in man, for instance, corpora lutea of pregnancy or ovulation less than 1 cm. in diameter commonly have cavities (Dubreuil and Riviere, 1947) and vesi- cular corpora lutea are relatively common in the cow (Hammond, 1927). These observations mean that the hypothesis of vascular limitation is untenable. Secretion of fluid by the follicle wall continues for
Discovery reports (1962) Discovery reports discoveryreports31inst Year: 1962 360 DISCOVERY REPORTS of pregnancy which was 19 cm. in diameter lacked a cavity. Conversely, cavities are found in the much smaller corpora lutea of other animals; in man, for instance, corpora lutea of pregnancy or ovulation less than 1 cm. in diameter commonly have cavities (Dubreuil and Riviere, 1947) and vesi- cular corpora lutea are relatively common in the cow (Hammond, 1927). These observations mean that the hypothesis of vascular limitation is untenable. Secretion of fluid by the follicle wall continues for an appreciable time after ovulation and vesicular corpora lutea in other mammals are usually attributed to the continued secretion of liquor folliculi by the ruptured follicle after the aperture has become closed (Brambell, 1956, p. 474). According to Robinson (1918) the persistence of the central cavity in the ferret depends on the degree of separation of the internal limiting membrane at ovulation. The point of rupture of the follicle is closed by a tenacious coagulum, the tertiary liquor folliculi, which also redistends the collapsed follicle often to the size it originally was before ovulation (Harrison, 1948). 30 20 /__ IO 1 1 1 1 1 1 1 1 9 10 11 u 13 CL. DIAMETER IN CMS. 9 10 II \2 CL DIAMETER IN CMS Text-fig. 9. a, Relation between cavity diameter and corpus luteum diameter, b, Relation between corpus luteum size and the incidence of cavities. The appearance of fin-whale corpora lutea of the vesicular type suggests that they are usually formed in this way. In most corpora with large cavities (Text-fig. 5 h-k) the stigma is inconspicuous and there is no eversion of luteal tissue to form a corona. This suggests that the aperture became closed again after ovulation and remained closed. The corpus illustrated in Text-fig. $k has a small stigma, but the corpus has a distended appearance and the luteal tissue has obviously been subjected to pressure from inside, presumably
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