110 LEONELL C. STRONG 



Tabulation 

 Normal 481 negatives : 34 reactions ±3.80 or 6.60% ± 0.74 



Gonadectomized 453 negatives : 7 reactions ±1.77 or 1.52% ± 0.39 



Difference 5.08% ± 0.83 



The difference is thus 6.12 times its probable error 



The operation on adult individuals therefore decreases the 

 percentage reactions significantly. 



We can study the results better if we compare the life-cycle 

 susceptibility for gonadectomized individuals with that for 

 normal mice (fig. 27). 



The first point for the gonadectomized curve is determined 

 by 102 observations; that for the fifth point, 42. The data for 

 the other three points have been given in the preceding three 

 charts. It is needless to emphasize the fact that the two curves 

 are directly each other's opposite. Whether this result is due 

 to the absence of the gonads or to the effects of th^ operation 

 alone remains to be proved. It is hard to understand how the 

 effect of the operation (shock, etc.) could have such a differen- 

 tial effect on mice from the various age groups. 



0. Influence of operation. In an attempt to analyze the effect of 

 the operation alone upon the susceptibility toward transplantable 

 tumor tissue, the mice are classified, regardless of age, according 

 to the length of time which had elapsed between operation and 

 inoculation. For convenience the arbitrary classes of to 5 

 days, 5 to 10 days, and 10 to 15 days after operation were chosen. 

 This experiment includes only individuals inoculated for the 

 first time. 



Tab^dation 



Controls 789 negatives : 80 reactions ±5.75 or 9.21% ± 0.66 



Group 1, 0- 5 days 177 negatives : 14 reactions ±2.43 or 7.33% ± 1.27 

 Group 2, 5-10 days 207 negatives : 4 reactions ±1.32 or 1.90%, ± 0.62 

 Group 3, 10-15 days 194 negatives : 8 reactions ±1.87 or 3.96% ± 0.93 

 Differences: 



Controls-Group 1 1.88% ± 1.43 or 1.31 times probable error 

 Controls-Group 2 7.31% ± 0.91 or 8.10 times probable error 

 Controls-Group 3 5.25% ± 1.14 or 4.60 times probable error 

 Group 1-Group 2 5.43% ± 1.41 or 3.85 times probable error 

 Group 2-Group 3 2.06% ± 1.11 or 1.86 times probable error 

 Group 3-Group 1 3.37% ± 1.58 or 2.13 times probable error 



