CYCLIC CHANGES IN UTERUS AND OVARIES. 17 



animals also some degenerative changes occur in the uterine 

 epithelium, but they are less marked than in animals which had 

 copulated. An examination of the uterus permits us in most 

 cases to determine whether or not ovulation had taken place at 

 the time of the examination in a guinea-pig in which copulation 

 had been prevented. 



From now on, the condition of the uterus is similar in both series 

 of guinea-pigs; the mitoses migrate from the surface epithelium 

 to the gland fundi and disappear completely in the epithelium 

 five to six days after the ovulation. The connective tissue pro- 

 liferation starts on the fourth day and ceases seven days after 

 ovulation. On the eighth day we find a beginning disintegration 

 of cells in the upper part of the connective tissue of the mucosa. 

 The later stages were also examined in the first series in animals 

 in which after copulation, pregnancy had been prevented through 

 an early ligature of the tubes. From the sixth to the twelfth 

 day after ovulation the epithelium is without mitoses; they then 

 begin to reappear in the surface epithelium. Notwithstanding 

 the presence of mature follicles, the uterus does not assume the 

 characteristic features of the uterus during heat. These changes 

 occur only after signs of degeneration have begun to set in the 

 corpora lutea. 



During pregnancy the uterine epithelium is relatively low, 

 mitoses occur only in the surface epithelium. The connective 

 tissue layer is thin and no mitoses are found in the connective 

 tissue cells. The uterus is therefore in a resting condition during 

 pregnancy. 



III. THE EFFECT OF EXTIRPATION OF THE CORPORA LUTEA 

 ON THE CYCLIC CHANGES IN THE UTERUS. 



In a previous communication we have shown that extirpation 

 of the corpora lutea within the first week after ovulation leads 

 in the majority of cases to an acceleration of the next ovulation. 

 In nine cases in which pregnancy was not present at the time of 

 the examination, the ovulation had not yet taken place not- 

 withstanding the complete extirpation of the corpora lutea. In 

 four of these cases the uterus had been split within the first 

 week after ovulation. In another case abortion had taken place 



