The structure and origin of corpora lutea in some of the lower vertebrata

Abstract

In Rana temporaria injection of a commercial preparation of gonadotropic hormone from pregnancy urine was not found to induce ovulation, but injection of acetic acid extract of anterior lobe of pituitary of the ox was followed by ovulation, when the controls had not ovulated. In Rana esculenta no ovulation occurred either after injection as above, or with acetic acid extract of ox anterior pituitary, or without injection. In Bufo calamita injections were made without result. In Xenopus laevis positive results of expts. on ovulation were obtained and sundry other expts. recorded. The structure of the ruptured follicles in Xenopus at 3 successive stages after ovulation is descr., and it is shown that reduction and absorption of the empty follicle begins immediately after rupture and proceeds rapidly, no true corpus luteum being found. The history of the ruptured follicle in the oviparous Lacerta viridis is compared with its history in the 2 viviparous forms, Anguis fragilis and Zootoca vivipara. The follicle immediately after rupture in the 1st case is very similar to that in the other, a collapsed sac with wide aperture, containing the follicular cells. In Lacerta the aperture closes and the mass of follicular cells begins to undergo absorption and reduction. In Anguis and Zootoca the closed follicles persist without signs of absorption during the development of the embryos in the oviduct, forming a structure essentially similar to the corpus luteum of the mammal. It is concluded that the fertilized ova within the oviduct give off substances which are absorbed by the blood and act as hormones which cause the persistence of the discharged follicles as corpora lutea, and that these hormones cause either directly, or indirectly through substances given off from the corpora lutea, the inhibition of ovular development and ovulation.