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SUMMARY
The uterine fluid of mice killed 2–6 hr after coitus and ovulation amounted to about 0·1 ml. and contained about 20 million spermatozoa and virtually no leucocytes. By 14–18 hr after coitus the leucocytes had increased to about 25 million and the spermatozoa had decreased to about 11 million, most of which were undergoing phagocytosis. Approximately 20 hr after coitus the uterine contents are apparently evacuated, in spite of the continued presence of a copulation plug. Phagocytosis of spermatozoa was also observed in rats but was much less extensive; this is considered to be because evacuation takes place sooner after ovulation, though still about 20 hr after coitus. The phagocytes were nearly all polymorphonuclear leucocytes.
Leucocytic invasion of the uterine lumen seems to occur mainly because of the distension of the uterus with fluid and not because spermatozoa are present. No evidence was obtained that either spermatozoa or leucocytes pass from the lumen into the uterine wall.
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Ovulation in mammals is followed by profound changes in the morphology and physiology of the genital tract, and it is now well established that this transformation is dependent upon a swing in the balance of the follicular and luteal hormones. It may be supposed that the functional and anatomical state of the organs at any time during the cycle is suited to the requirements of the moment, so that the proper transport of gametes, fertilization and implantation, would not be expected at other than the normal times.
On the other hand, Pincus & Enzmann [1936] claim to have achieved fertilization of rabbit eggs in vitro by a simple technique. They, and numerous other workers, have succeeded in culturing fertilized eggs to the early blastocyst stage. There have been many reports of naturally occurring ectopic pregnancy in a variety of animals and, on the experimental side, Nicholas [1933, 1934] and others
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In the course of investigations on the frequency of fertilization in immature rats which had been caused to ovulate by the injection of gonadotrophins, it was observed that a remarkably large number of eggs from unmated rats had divided so as to simulate segmentation very closely. Fragmentation resembling segmentation in tubal as well as ovarian eggs is a well-known phenomenon, but there is little specific information on the frequency with which it occurs.
Kampmeier [1929], who reviewed the early literature, stated that it was first reported by Pflüger in 1863 in ovarian eggs. Numerous papers have since appeared giving details of nuclear and meiotic changes observed. Kingery [1914] studied the eggs in atretic follicles of immature mice and found abnormal maturation spindles but no segmentation spindles. He frequently observed eggs with several or numerous 'cells', but these contained abnormal, several, or no nuclei. Loeb [1932] reported the finding of embryonal
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It was shown by Smith & Engle [1927] and Engle [1927] that ovulation could be induced in adult rats and mice by the daily implantation of anterior pituitary tissue. The numbers of eggs which were obtained by this process, from twenty to forty-eight from each animal, were well in excess of those observed after spontaneous ovulation. Furthermore, when mice treated in this way were mated many of them became pregnant and were found to have from nineteen to twenty-nine implanted embryos. These results seemed to hold promise that a method might be developed for materially increasing the prolificacy of animals, a procedure which would be valuable if it could be applied to certain classes of livestock.
The method was simplified by Cole [1936] who was able to induce the ovulation of up to fifty-four eggs with a single injection of unfractionated pregnant mares' serum. He also noted that immature rats
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SUMMARY
Stilboestrol was administered in the drinking water at several different concentrations to groups of normal adult rats and mice.
Continuous vaginal cornification was obtained with the higher dose levels and both species showed a capacity for repeated coitus at intervals corresponding approximately to those separating oestrous periods in untreated animals. The response was much more uniform in the mice.
Inhibition of ovulation required dose levels well above those that clearly influenced the nature of the vaginal smear. The great majority of ovulated eggs were found to undergo spermatozoon penetration, and supplementary spermatozoa were commonly seen. Results suggest that the frequency of spermatozoon penetration was increased by moderate oestrogen dosage. Fertilization appeared to be quite normal.