IT HAS BEEN REPORTED (McKenzie and Terrill, 1937; Bell, Casida, and Darlow, 1941; Quin and Van Der Wath, 1943) that the ovariectomized female sheep and goat are brought into estrus uniformly and promptly by a single injection of estrogen, a result confirmed at this Station (unpublished results). In this respect both animals differ from the common laboratory mammals (guinea pig, rat, and mouse) which require progesterone following estrogen priming for the regular exhibition of estrus. The marked difference in response to estrogen in the respective species indicates that the mechanisms involved in the induction of estrus are not identical. Since female sheep and goats exhibit a well-defined period of seasonal anestrum, it was thought that this factor might possibly be associated with the variations cited. The descriptions of the breeding habits of tne golden hamster given by Bruce and Hindle (1934), Deanesly (1938) and Peczenik (1942), and our own observation that it failed to breed from.
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Frank et al. (1945) studied this question.