CAUSE OF HYPERTROPHY OF SURVIVING OVARY 71 



The average total number of ova in the right ovaries in both 

 series removed at twenty days from the sixteen semispayed rats 

 is 5405, while that of the ova in the sm-viving left ovary is 5207. 



Thus the number of ova in the right ovaries at the age of 

 twenty days is somewhat greater than at the end of the experi- 

 ment, though the difference amounts to less than 4 per cent in 

 favor of the younger ovary. This is what we should expect. 

 We have already found (table 3) that the surviving ovaries have 

 grown very much and are from two to ten times heavier than 

 the right ovaries, removed at twenty days. Despite the fact 

 of this great difference in their weights, the numbers of ova in 

 these two groups of ovaries are nearly the same. I conclude 

 again, therefore, that the total number of ova in the surviving 

 ovary is not a factor in the compensatory hypertrophy. 



When we compare the number of ova in the left surviving 

 ovaries of the semispayed with that in the corresponding left 

 ovaries of the controls, at the same age, we find that, though 

 there are individual variations, the surviving ovaries have on 

 the average a less number of ova than those in the control rats. 

 This relation can be seen from tables 7 and 8. Thus the differ- 

 ence in the number of ova between these two kinds of ovaries 

 (control and semispayed) is 12 per cent in favor of the control, 

 despite the fact that the surviving ovary is much heavier than the 

 control. I therefore conclude that the total number of ova is not 

 the cause of the compensatory hypertrophy of the ovary. 



As is shown in table 7 the control rats in series I (with males) 

 possess a smaller number of ova than the controls of series II 

 (without males) being 5579 and 6274, respectively, though the 

 corresponding difference between the numbers in the semispayed 

 rats in series I and series II is very slight: 5150 and 5265 ova, 

 respectively. 



As a rule, the total number of ova decreases according to the 

 growth (age) of the ovary, and therefore it may be possible that 

 the presence of male rats in series I in some way accelerates the 

 normal growth of the control ovary, thus reducing the number 

 of ova present. 



