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THE AMEBIC AN NATURALIST [Vol. LY 



Sex as a Factor in Resistance 

 In attempting to analyze the difference in the length 

 of life following inoculation, we will consider first a num- 

 ber of possible factors other than heredity. It will be 

 convenient to start with sex. Chart 1 shows the per- 







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C//A 



RT 























































centage of the males and females alive at the beginning 

 of each day in lots 10 to 14, starting with 100 per cent, on 

 the fifteenth day after inoculation. The males have some 

 advantage in lots 10-14, but it is too small to be of more 

 than doubtful significance. In lots 3 to 9, moreover, the 

 two mortality curves keep crossing each other in such a 

 way as to indicate that sex makes no appreciable differ- 

 ence in resistance. 



The Age of the Dam as a Factor 

 Some rather dubious indications of a relation between 

 age of mother and susceptibility of the offspring to tuber- 

 culosis were found by Pearson among human beings. 



