1 38 INTERNAL SECRETIONS OF THE OVARY 



experiments. If the initial growth of the uterus of the dog had 

 begun when the folhcles were ruptured, the removal of the 

 follicles might have led to the immediate onset of prooestrous 

 degeneration. The inhibitory effects produced in the later 

 experiments might be due to the severity of the operation or to 

 the formation of luteal tissue by the ruptured follicles (see p, 

 184). There is thus no direct experimental evidence that the 

 mature Graafian follicle is the essential factor in the production 

 of oestrus. 



Evidence is now available which shows quite definitely that 

 the maturation of Graafian follicles is not necessary for the 

 occurrence of oestrous symptoms in the accessory organs. Blair 

 Bell (56) long ago reported experiments where the grafting of 

 rabbit ovaries from which the cortical areas had been removed 

 resulted in the appearance of oestrus in the host. Since the 

 cortical areas would contain the majority, if not all, of the 

 Graafian follicles, these experiments provided a hint that 

 the follicles were not essential for the appearance of oestrus. 

 The really critical experiment, namely, the investigation of the 

 results of entire obliteration of the follicular system of the ovary, 

 has only recently been attempted. Possible means whereby 

 the ovarian follicles can be eliminated are few, and exposure to 

 X-rays is by far the most certain technique. The action of 

 X-rays on the ovary has been studied to some extent physiolo- 

 gically, and in detail histologically, for many years, and it was 

 soon found that the Graafian follicles and, indirectly, the 

 corpora lutea could be eliminated. Their elimination has been 

 shown to have no effect in inhibiting the development of the 

 accessory organs in the immature animal, or in causing atrophy 

 of the accessory organs in the adult. The early w^orkers on the 

 effects of X-ray sterilization appear to have made no observa- 

 tions on its effects on the occurrence of the oestrous cycle. 

 Recently, however, this problem has been investigated in detail 

 (492-5), and it is possible to state quite definitely that the en- 

 tire elimination of the whole follicular system neither inhibits 

 oestrus, nor interferes with its normal periodicity. 



Histological effects of exposure to X-rays. Early work on the 

 histological effects of exposure of the ovary to X-rays was 

 carried out by Halberstadter (261) and by Fellner (190) on the 



