SUSCEPTIBILITY TO TRANSPLANTABLE TUMORS 127 



5. Gonadectomy 



The discussion of this part of the paper should have followed 

 the experiments dealing with age, but since the sex factor is 

 primarily a secondary phenomenon of age, it was thought best 

 to discuss that subject immediately following the age factor. 



Several recent experiments have been performed dealing with 

 the effects of gonadectomy upon susceptibility to transplant- 

 able tumors. As an example may be mentioned the work of 

 Sweet, Corson-White, and Saxon ('13). They employed adult 

 male individuals only. The conclusion was reached that castra- 

 tion had two effects upon susceptibility to transplantable tumor : 

 1) the number of individuals that grow the tumor progressively 

 was significantly increased and, 2) the rate of growth of the mass 

 is materially increased. It is well to point out, however, that 

 market mice of unknown ancestry were employed; the results 

 are, therefore, in all probability, not very simple to interpret. 

 It is also very diff.cult to conclude anything about female be- 

 havior to gonadectomy from the study of male individuals alone. 



In our own experiments we have been unable to verify the re- 

 sults obtained by these investigators. In the first place, we 

 determined that somehow or other the effects of the operation 

 alone had some unexpected influence upon tumor susceptibility. 

 Individuals that are inoculated five to ten days after operation 

 give a significantly lower percentage of reaction masses than do 

 individuals inoculated at any other time interval after the opera- 

 tion. The percentage reactions of the dBrB tumor for individuals 

 inoculated from zero to five days after operation was found to 

 be 7.33% rt 1.27; that for individuals inoculated from five to 

 ten days, 1 .90% ± 0.62, and that for animals from ten to sixteen 

 days, 3.96% ± 0.93. The first time group (0 to 5 days) is not 

 significantly different from that obtained for the control mice, 

 9.21% ± 0.66 (difference 1.88% ± 1.43 or 1.31 times probable 

 error). Individuals from the five-to-ten-day time interval groups 

 gave remarkably few reactions. They are distinctly more resist- 

 ant to the transplantable tissue than are the controls (difference 

 in favor of the gonadectomized 7.31% ± 0.91 or 8.10 times its 



THE JOURNAL OP EXPERIME>rrAL ZOJLOGY, VOL. 33, NO. 1 



