Abstract
In a recent series of papers 1 we have described the preparation and effects of an extract made from the corpora lutea of swine. When administered to recently spayed adult rabbits, or to immature rabbits whose uteri have been brought to the mature resting state by injections of oestrin, the corpus luteum hormone (progestin) induces alterations of the endometrium characteristic of pregnancy. If female rabbits are mated and castrated 18 hours later, while the fertilized ova are still in the Fallopian tube, the extracts substitute for the removed ovaries so completely that the embryos are nourished, become implanted, and develop in the uterus exactly as in normal pregnancy under the influence of the mother's own corpora lutea. In the third of our previous reports we have described 2 animals which were carried to the 13th and 19th days of pregnancy respectively. The demonstration of normal implantation with normal foetuses in these animals at autopsy led us to attempt to carry other animals through the full term, with the results now to be reported.
The procedure in general was as follows: A doe was mated, usually to 2 bucks, and was subjected to bilateral double oöphorectomy 18 hours after mating. The number of ruptured follicles in each ovary was noted. Administration of the extract by subcutaneous injection was begun on the day of operation and was continued daily thereafter. The preparation used was the crude oily extract described in our second paper. About the 8th to the 12th day of the experiment the animal was again explored under ether anesthesia, for the purpose of determining whether or not implantation had taken place. This procedure enabled us to conserve the costly extract in case the pregnancy had not continued.
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