L. DONCASTER AND F. H. A. MARSHALL 71 



elusive kind is difficult to obtain in man, since even if children of both 

 sexes are bom after single ovariotomy, it is rarely possible to prove that 

 the ovary has been completely removed. It therefore seemed worth 

 while to test the matter critically in some other mammal, and with that 

 object the experiments described below were made on rats. 



Two female albino rats were taken, and in May 1910 the right ovary 

 with the greater part of the fallopian tube was removed from one of 

 them, and the same parts from the left side of the other. Both animals 

 rapidly recovered from the operation and on being put with a buck, 

 shortly became pregnant. The female from which the right ovary was 

 removed gave birth to seven young on July 8. The young all died soon 

 after birth, and one of them was almost entirely eaten by the mother. 

 The rest were preserved for examination, and it was found on dissection 

 that there were four females, one male, and one was too much decom- 

 posed before being preserved for its sex to be determined with certainty; 

 it appeared to be a female. 



The rat from which the left ovary had been removed gave birth to 

 five young on July 28 ; one young died shortly after birth ; it was dis- 

 sected when quite fresh and proved to be a male. The remainder lived 

 until August 22 when they were killed and dissected ; there were three 

 females and one male, giving three females and two males in all. On 

 the same day the two rats which had been operated on were killed and 

 dissected. In neither could any trace of ovary or ovarian tissue be 

 found on the side from which the ovary had been removed. In that 

 from which the left ovary was taken out there was about ^ inch of 

 fallopian tube, ending apparently blindly; in the other the right 

 fallopian tube had been cut ofif at its junction with the uterus. In each 

 case the uteri were normal. They were congested on both sides in the 

 rat lacking the right ovary, which was probably on heat at the time of 

 killing. In the female (left ovary removed) which had suckled its 

 young up to the time of killing all the mammae on both sides were 

 normal and functional. In both rats the remaining ovary was ex- 

 ceedingly large, and had doubtless undergone compensatory hypertrophy 

 in consequence of the removal of the ovary of the other side^ The 

 relatively large size of the litters (7 and 5) produced from one ovary 

 may be thus accounted for. That the litters were produced from one 

 ovary in each case is further shown by the fact that on microscopic 

 examination it was found that in the rat from which the right ovary was 



^ Cf. Carmichael and Marshall, Journal of Phytiology, voL xxxvi. p. 431. 



