298 SHINKISHI HATAi 



The total number of litters used by Stotsenburg for the spayed 

 series was 17. These comprised 38 spayed and 35 control rats. 

 In the case of semi-spayed there were 12 Utters comprising 25 

 semi-spayed and 23 control rats. 



. A few of these litters however lost either some of the operated 

 animals or of the controls before my examination, also some of 

 the organs were used for histological preparations, so that the 

 number of litters, as well as number of individuals represented in 

 the present tables is less than that given by Stbtsenburgin his 

 paper. 



On the other hand it is important to state in this connection 

 that all of the animals from which complete data were obtained 

 were also used in making the present tables. For determining 

 the modification in the operated groups, the following method 

 was adopted: 



First the percentage deviation of the controls from the calcu- 

 lated values for any character as given by the formulas, was 

 determined and then the corresponding percentage deviation of 

 the operated animals. The algebraic difference of the two values 

 thus obtained gives the difference between the operated and con- 

 trols. In the tables here given the body length was always taken 

 as the basis for comparison. 



The values obtained, are given in the accompanying tables 

 and designated as "Percentage by which the operated animals 

 differ from the controls." This method is necessary since the 

 observed body length which is taken as the basis for the weight 

 of the organs is only rarely identical in both operated and controls, 

 and thus a direct comparison of the observed values is rarely 

 justified. 



CASTRATION 



This experiment is based on 11 litters comprising 25 castrated 

 and 12 control rats. The series was divided into four groups 

 each containing 3 litters — except one group, containing 2 litters. 

 In every case the operated and control rats which are com- 

 pared belong to the same litter. This precaution minimizes 

 the variabiUty of the characters under consideration, since the 



