EFFECTS OF OVARIECTOMY IN THE MARSUPIAL SETONIX BRACHYURUS

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Abstract
The effects of bilateral and unilateral ovariectomy performed on various days of the delayed cycle are described and it is concluded that the corpus luteum is essential for the resumption of embryonic development and for induction of the secretory phase in the endometrium. It can wholly fulfill these functions by Day 7 and is not necessary for the subsequent progress of pregnancy. The corpus luteum after Day 2 also inhibits premature follicular development and ovulation from the remaining ovary in unilaterally ovariectomized animals. The first two of these functions of the corpus luteum, but not the latter one, have fully substituted with injections of progesterone given during the first 7 days of the cycle. Parturition failed to occur in all bilaterally ovariectomized animals and occurred in only one unilaterally ovariectomized animal. Birth occurred in two bilaterally ovariectomized animals given a relaxin preparation, but in none that was given either oestrogen or oxytocin. It is suggested that failure to give birth may be due to a lack of relaxin secretion after ovariectomy and a consequent inadequacy of the pseudo-vaginal canal for parturition.