CAUSE OF HYPERTROPHY OF SURVIVING OVARY 75 



Ovulation in the semispayed 



As to the time of the first ovulation (table 1), the semispayed 

 do not differ from the control rats. The first ovulation takes 

 place invariably when the body lengths of rats reach 148 to 

 150 mm. In my previous paper ('20) I have presented the data 

 on the first appearance of ovulation and found that it occurs 

 when the rats attain this body length. It is worthy of note 

 that despite the greater activity within the surviving ovary, 

 nevertheless the first ovulation occurs at the same time in both 

 the hypertrophied and control ovaries. Whether or not this 

 fact indicates that the stimulus which induces the first spontane- 

 ous ovulation originates outside of the ovary needs further study, 

 but it may not be amiss to call attention to the fact that in the 

 rat the thymus gland attains nearly its maximum weight at the 

 same period, sixty to seventy days, at which ovulation appears 

 (Donaldson, '15, chart 23, table 72) and that the characteristic 

 sex difference in the weights of both the suprarenals and of the 

 hypophysis also become evident at this age. 



Body growth in the semispayed 



Stotsenburg ('13) reported that removal of both ovaries from 

 young female albino rats causes the body weight of the spayed 

 females to be increased 17 to 30 per cent above that of the con- 

 trols; however, in the case of semispaying, he found no change 

 in the growth between the operated and the control rats. Moore 

 ('19), in his experiments with albino rats, transplanted gonads, 

 interprets his results as showing that removal of the ovaries 

 increases the growth rate of the female. 



Biedl ('12, translated by Forster) states that as the results 

 of exposure of the ovary to the action of the Rontgen ray the 

 genitals are atrophied, accompanied also by diminution in the 

 size of the ovaries and a disappearance of Graafian follicles, while 

 the interstitial cells persist. Biedl infers from this reaction that 

 the Graafian follicles are responsible for preventing the uterine 

 atrophy. 



THE AMERICAN JOURNAL OF ANATOMY, VOL. 28, NO. 1 



