THE PERIODICITY OF (ESTRUS 143 



brana granulosa cells of primordial follicles. The adult ovary 

 does not show proliferations from the germinal epithelium after 

 sterilization. Such an ovary differs, therefore, from that of the 

 sterilized immature animal in consisting of tissue of follicular 

 derivation. No signs of periodic change have been observed in 

 this tissue once a stable condition has been reached; the histo- 

 logical periodicity appears to be destroyed as completely in the 

 adult as in the immature animal. The abnormal luteal type of 



Fig. 49. — Uterus of Mouse sterilized at weaning time by 

 Exposure to X-rays, showing typical cestrous Condition 

 {cf. fig. 22). 



ovary is found onl}^ rarely in the sterilized adult. The effects 

 of exposure to X-rays in adequate dosage may therefore be 

 summarized as follows: 



(a) Destruction, and in the immature animal complete 

 reabsorption, of the Graafian follicle, and indirect 

 elimination of the corpora lutea. 



(h) Complete elimination of cyclic histological changes. 



Effect of X-ray sterilization on the cestrous cycle. Mice in which 

 the entire follicular system has been destroyed by exposure to 

 X-rays, show the typical cestrous changes in the accessory organs 

 at the same periodicity as the normal female. Sterilization (492-5) 

 has been described at three ages — {a) just before or at the time 

 of birth, (h) at weaning, [c] at maturity. In mice irradiated at 

 weaning time, puberty occurs at the normal date, namely, 6-7 



