74 HAYATO AUAl 



larger number degenerate. By this process the surviving ovary 

 comes to contain a greater number of these folUcles, and on this 

 account is heavier. After puberty there is added to these changes 

 the more rapid formation of corpora lutea which contributes in 

 a striking way to the hypertrophy of the surviving ovary. 



I may repeat here that the growth of the stroma in the sur- 

 viving ovary appears to be about the same as in the control. 

 A shght increase is shown during growth, but it is certain to my 

 mind that this tissue plays no important role in the compensatory 

 hypertrophy. 



On the reproductive power of the semispayed 



If the numbers of large corpora lutea are taken as an index 

 of ovulation, then in table 6 (last litter in series 1 and last two 

 Utters in series 2) we note a total of sixty-eight corpora lutea 

 in the semispayed and twenty-nine in the corresponding controls, 

 or about two to one. This would suggest that for some reason 

 the surviving ovary was discharging ova about twice as fast as 

 the control ovary. In support of this conclusion are the obser- 

 vations of both Doncaster and Marshall ('10) and of King ('11) 

 who found the litter number from semispayed females approxi- 

 mately that for the control normal rats. The former investi- 

 gators also checked the litter number by the number of fresh 

 corpora lutea and found the relations which were to be expected. 



As has been noted. Bond is of the opinion that in rabbits 

 copulation may be the stimulus in producing the hypertrophy 

 of the surviving ovary. However, I have been able to show 

 that the semispayed rats which were absolutely separated from 

 the males (series II) show a compensatory hypertrophy just as- 

 perfect as those which were kept with the males (series I). 

 Therefore, in the rat at least, we should seek some other source 

 for the stimulus. 



