A Practical Test for Potency of Extract of Corpora Lutea.

a suitable test for potency. Corner's and Allen's' studies on progestational proliferation in the rabbit, resulting from the physiological action of their extract of the corpus luteum, and Hisaw's and Leonard's2 similar results, provided a useful test, but one which had several practical objections, arising primarily from the relatively large size of the test animal, and the consequent expense of obtaining and maintaining the animals and of making the tests. To overcome these objections, W. M. Allen3 attempted to transfer the application of this technique, using rats as test animals. As a result of thorough studies, he concluded that "The histological alterations of the rat's endometrium during pseudopregnancy are insufficient to warrant the use of these changes as a test for corpus-luteum extracts." At the same time we obtained wholly confirmatory, though as yet unpublished, results in this laboratory. We also had similar results in studies conducted on the uterus of