Etudes sur la pseudo-gestation et l'aestrus prolonge apres injection de fortes doses d'jestradiol chez la rate adulte RE'SUME'.-TOUS les animaux ont ete examines a des moments diff6rents au cours des trois semaines qui suivirent les injections.L'originalite de cet article consiste dans le fait que des transformations endometriales ont ete observees au cours de la phase pseudo-gestative bien connue. Cette phase suit immediatement les injections. Ensuite la muqueuse uterine reprend son aspect cestral ou dicestral. Des faits similaires, mais moins accentues, ont ete observes dans les memes conditions chez des animaux castres.L'cestrus continu, qui succede immediatement aux transformations de pseudo-gestation de la muqueuse vaginale, est caracterise par la croissance d'un grand nombre de follicules jeunes et par la maturation kystique de certains autres. La membrane folliculaire de certains peut se plisser. Ceci a une cause ovarienne.Il faut remarquer egalement les stades intermediaires qui apparaissent entre ces deux phases dans le vagin.Quatre animaux ont eu une hemorragie du type post-cestral dans la lumiere vaginale.Studies on Pseudogestation and Prolonged CEstrus after Injection of Large Doses of CEstradiol in Adult RatsSummary.-All the animals were examined at different times during the three weeks that followed the injections.The originality of this paper consists in the observation of endometrial retrogressive transformations during the well-known pseudo-pregnant phase.This phase immediately follows the injections and at its end the uterine mucous membrane resumes its oestrous or dicestrous state. Similar, but less marked, appearances have been noticed in the same conditions in castrated animals.The continued cestrus, that immediately follows the changes of pseudo-pregnancy in the vaginal mucosa, is characterized by the growth of a greater number of young follicles and the cystic maturation of some others: the follicular wall of some of them can become wrinkled. This has an ovarian cause.Intermediate states also appeared between those two phases in the vagina.Four animals had haemorrhage in the vaginal lumen; the haemorrhage was of a postcestrous type.