INTERNAL SECRETION OF CORPUS LUTEUM 177 



and the guinea-pig, the removal of the corpora lutea of ovulation 

 expedites the appearance of the next oestrous period. Thus, 

 Loeb (390) found that their removal in the guinea-pig led to the 

 appearance of the next oestrus at about the fourteenth day 

 instead of at the twentieth day. Loeb (400) also found that 

 the removal of the corpora lutea during pregnancy did not 

 always result in the immediate termination of gestation. 

 Ovulation, however, very soon followed the operation whether 

 or not the foetuses remained temporarily. 



Hammond (265), by squeezing out the corpus luteum from the 

 ovary of the cow, was able to cause the next oestrous period to 

 occur at the ninth day instead of the twentieth day. In the 

 mouse (494), however, indirect elimination of the corpora lutea 

 by exposure to X-rays does not bring about an earher appear- 

 ance of the next oestrus. This is due to the fact that in this 

 animal the dioestrous interval is very short, and practically no 

 development of the corpora lutea to a functional stage takes 

 place in the ordinary unmated cycle. In other words, the 

 unmated mouse possesses no luteal phase in the cycle, and 

 therefore the elimination of the corpora lutea cannot suppress 

 such a phase. After sterile copulation, however, when the 

 cycle in the mouse does possess a luteal phase, the ehmination of 

 the corpora lutea hastens the reappearance of oestrus. Thus, 

 in certain mice, ovulation may temporarily be in abeyance at 

 oestrus so that no corpora lutea are formed. In such animals 

 pseudo-pregnancy is not found (500) . In the cow and the guinea- 

 pig the luteal phase is prominent and its elimination, therefore, 

 leads to the earlier appearance of the next oestrus. 



Similar conclusions may be drawn from converse experiments, 

 namely, from the experimental prolongation of the functional 

 life of the corpus luteum. Correlated with this there is found 

 a prolonged disappearance of oestrous changes both in the ovary 

 and in the accessory reproductive organs. Thus, Loeb (^01) 

 found that hysterectomy in the guinea-pig causes the corpora 

 lutea to remain intact and functional for a long period. This 

 condition is accompanied by a cessation of the oestrous cycle. In 

 the cow various workers, including Hess (298), Wilhams (638), 

 and Tandler (608), have found that the persistence of corpora 

 lutea results in sterihty, owing to the suppression of ovulation. 



P.S.O. M 



