SUSCEPTIBILITY TO TKANSPLANTABLE TUMORS 109 



n. Age susceptibility in normal and gonadectomised mice. The 

 next experiment was to determine whether there is any differen- 

 tial effect of gonadectomizing individuals from the different age 

 groups. Unfortunately, the number of individuals from class 1 

 and class 5 that were operated on were small, so that no valid 

 comparison can be made for these groups. Figure 24 (p. 107) 

 shows that the percentage reactions for group 2 individuals is 

 somewhat lower than the controls, but not significantly so. 



Tabulation 

 Class 2 normals 87 negatives : 10 reactions ±2.02 or 10.31% ± 2.08 

 Class 2 Gonadect. 468 negatives : 28 reactions ±3.47 or 5.65% ± 0.69 



Difference 4.66% ± 2.19 



The difference is thus 2.13 times its probable error 



If the depressing effect of the operation is taken into con- 

 sideration, there is, in this age group, no difference between nor- 

 mals and gonadectomized individuals in their susceptibility to 

 transplantable tumor tissue. Class 3 individuals gave quite 

 unexpected results. The gonadectomized individuals showed 

 a significant increase over the controls. In this one age group 

 (class 3) there was apparently no depressing effect of the opera- 

 tion encountered (fig. 26, p. 111). 



Tabulation 

 Gonadectomized 197 negatives : 28 reactions ±3.34 or 12.44% ± 1.49 

 Normals 146 negatives : 10 reactions ±2.06 or 6.41% ± 1.32 



Difference 6.03% ± 1.98 



The difference is thus 3.05 times its probable error 



It may be recalled that the normal class 3 individuals gave 

 the minimum percentage reactions. Just why we should get 

 the greater increase in percentage indications for individuals 

 in this group of gonadectomized mice is not clear at present, but 

 will be considered again later. 



With individuals of group 4 just the reverse is found. Very 

 few gonadectomized adult mice show any indications whatever 

 of a favorable reaction (fig. 25, p. 111). 



