144 INTERNAL SECRETIONS OF THE OVARY 



weeks of age, and the subsequent periodicity of oestrus, though 

 shghtly erratic in certain instances, is reasonably normal. In 

 mice sterilized at an earlier age, the oestrous cycle tends to be 

 more abnormal. This is due to the fact that abnormal histo- 

 logical effects, such as the luteinization of the cells derived from 

 the germinal epithelium, are more often found. In such animals 

 the cycle is either absent or ceases after a transitory appearance. 

 In most sterilized adults the cycle in the accessory organs 

 persists quite unchanged. Table 9 shows the length of oestrus 

 and dioestrus in twenty mice before and after irradiation. 



5 7 9 11 13 IS 17 



Leng-th in days of cycle 



19 



21 



23 25 



Fig. 50. — Frequency Polygons for length of Oistrous Cycle 

 before and after x-ray sterilization. 



No significant change is observable. 



In all these animals histological examination of the ovaries 

 showed that no Graafian follicles whatever were present. The 

 component parts of the cycle, namely dioestrus, prooestrus, 

 metoestrus, and oestrus, were all found to be normal. The only 

 unusual feature of the post-irradiation cycle is its slightly 

 greater variability in length; it is quite evident that this in no 

 way detracts from the general conclusion that the complete 

 destruction of the follicular system of the ovaries does not 

 inhibit the occurrence of oestrus. Zondek (647) has reported 

 similar results. 



Analysis of the experimental results from X-rayed animals 

 shows that the oestrus-producing hormone is probably elaborated 

 by the first post -irradiation proliferation from the germinal 

 epithelium in animals sterilized while immature, and by the 

 amorphous tissue of follicular derivation in those sterilized when 

 adult. In the former group the similarity of the proliferation 



