176 INTERNAL SECRETIONS OF THE OVARY 



could be readily removed, leaving intact the second ovary 

 containing no corpus luteum, to carry on the other ovarian 

 functions. Recently a technique has been elaborated whereby 

 the mouse can be converted to this type (499). This technique 

 consists in unilaterally sterilizing the young animal by X-rays. 

 When adult, corpora lutea are present only in one ovary, which 

 can be removed surgically without any adverse after-effects. 

 The other ovary, without corpora lutea, is capable of carrying 

 on the ovarian functions other than those associated with the 

 corpora lutea (see p. 143). 



(b) INHIBITION OF OVULATION AND CESTRUS 



The idea that the corpus luteum performs the function of 

 suppressing ovulation during pregnancy appears to have been 

 put forward originally by Beard (54) and by Prenant (520). 

 These authors based their conclusion on the general functional 

 correlation which is known to exist between the development of 

 the corpus luteum and the absence of oestrus. This correlation, 

 of course, is not found during the period of anoestrus, through- 

 out which ovarian activity, both follicular and luteal, is in 

 abeyance. This, however, is a special condition, and so far as the 

 ordinary ovarian cycle of the regular polyoestrous animal is 

 concerned, the persistence of the corpus luteum is invariably 

 associated with the absence of oestrus. 



A few authentic cases of superfoetation have been recorded 

 (see Smith, 571). These seem to show that ovulation may 

 occur during pregnancy, but the condition is very rare, and in 

 the normal animal the presence of a functioning corpus luteum 

 prevents ovulation. The exact extent to which follicular 

 maturation is inhibited by the functional corpus luteum seems 

 to show specific variation. In the guinea-pig, for instance, Loeb 

 (389) describes waves of follicular growth even during pregnancy. 

 This growth ends, however, in atresia, inhibition of ovulation 

 occurring in all species. During recent years the hypothesis put 

 forward by Beard and Prenant has been extended by a variety 

 of experimental studies, the more important of which are 

 summarized below. 



Functional correlation. In certain animals, such as the cow 



