CAUSE OF HYPERTROPHY OF SURVIVING OVARY 61 



the mother, together with the control females, and one or two 

 males of the same litter. 



On the other hand, the rats belonging to series II were also 

 returned to the mother after operation, but were kept with the 

 control females only, and thus were absolutely separated from 

 the influence of the males. 



In order to avoid a possible seasonal effect on growth, all the 

 eight litters were chosen from those born in the spring, from 

 February 15th up to April 8th, and the members of the litters 

 had approximately the same body weight, about 20 grams, at 

 the time of operation. 



I followed the technique employed by Stotsenburg ('13) for 

 removing the ovary; that is, while the rats were under ether the 

 hairs were clipped, then an incision was made along the edge 

 of the lumbar muscles, a little caudal to the last rib. The 

 incision need not be longer than 1 cm. and should not cause 

 bleeding, A small blunt hook is inserted through the opening 

 and the right ovary pulled out with the adherent structures and 

 cut from its attachment to the fallopian tube. The whole 

 operation takes but a few minutes. 



The edges of the wound are brought together and covered with 

 thin celloidin, and the animal is placed in warm cotton until 

 consciousness has fully returned, when it is replaced in the cage. 

 Beyond boiling the instruments, no other aseptic precautions 

 were taken, yet in no case did ill effects follow the operation. I 

 removed always the right ovary. 



Within one or two hours after the operation, the rats were 

 returned to the mother, and usually a week later the mother 

 was removed from the cage. The excised ovary was carefully 

 prepared and weighed in a small weighing bottle. After the 

 weight had been determined, the ovary was fixed in Bouin's 

 solution, embedded in paraffin, completely sectioned at 10 n, 

 and finally stained with hematoxylin and eosin. 



The operated rats with their controls were killed at the third, 

 fifth, sixth, and seventh weeks after operation; i.e., at 41, 55, 

 62, and 69 days of age. 



