ON THE MECHANISM OF OVULATION IN THE RABBIT IV. QUANTITATIVE OBSERVATIONS ON THE ACTION OF EXTRACTS OF URINE OF PREGNANCY

¹ Department of Physiology, University of Pennsylvania Medical School

1. The post-partum rabbit responds with great regularity to the injection of one minimal effective dose of an extract of urine of pregnancy.

2. Because of this regularity, and the rapidity and ease with which the results may be determined, it is recommended that the post-partum rabbit be given a trial in the bioassay of gonad-stimulating extracts.

3. Follicles discharged by one m.e.d. of an extract of urine of pregnancy undergo a process of luteinisation similar in rate and magnitude to that seen in pseudopregnancy. The lutein tissue produced in such artificially discharged follicles sensitizes the uterus for the production of decidual tumours.

4. In face of the data obtained from the experiments with repeated subminimal doses, it is impossible to explain the luteinisation of artificially discharged follicles solely on the basis of the storage and subsequent utilisation of some of the injected material.

5. It is possible to luteinise unruptured follicles in the rabbit ovary by the administration of an extract of urine of pregnancy at rate below that which is required to provoke ovulation.