310 SHINKISHI HATAI 



This observation is not new but the facts noted in this case 

 • furnish one more instance in a particularly clear form. 



Touching the enlargement of the ovary we note, for instance, 

 that Bond ('06) has shown in rabbits that a removal of one ovary 

 is followed by compensatory growth of the remaining ovary. 

 Bond however asserts that this compensatory growth takes place 

 only when the animals are allowed to become pregnant or at least 

 to have sexual intercourse. 



Carmichael and Marshall ('08) tested the question of compen- 

 satory growth by using rabbits also. The main conclusion reached 

 by them is that the compensatory growth of the ovary occurs 

 independently of both sexual intercourse and pregnancy; a con- 

 clusion contrary to that reached by Bond. This agrees however 

 with the results obtained by the present writer on the albino rat. 



By removing portions of the remaining ovary, Carmichael and 

 Marshall showed further that the power of compensatory growth 

 possessed by the remaining ovary is relatively greater the larger 

 the amount of ovarian tissue which has been removed. 



It is interesting to note that their method of determining the 

 amount of hypertrophy was to compare the weight of the remain- 

 ing ovary with that of the other which has been removed two to 

 five months earlier. The rabbits were fully grown at the time of 

 operation. Our study of the albino rats (Hatai '13) shows that 

 the ovary grows in weight even after the rats have become mature, 

 and consequently the amount of compensatory growth can only 

 be determined closely by knowing the amount of normal growth 

 during the period under consideration. 



Our results on the albino rats however indicate that the con- 

 clusion reached hy Carmichael and Marshall was essentially cor- 

 rect, as the amount of normal growth of ovarian tissue during the 

 several intervening months is probably not large in the adult 

 rabbits. 



Remarks on the weight of the hypophysis. It is to be noted that in 

 the albino rats the hypophysis presents a sexual difference which 

 is very marked (Hatai '13) as the hypophysis of the female is 

 more than twice as heavy as that of the male. In the Norway rats 

 the sex difference is very slight and probably still less, if present 



