512 



THE AMERICAN NATURALIST 



[Vol. LV 



of cancer not to heredity, but to infection, and as late as 

 1910 Bashford expressed the opinion that heredity has 

 no significance in the causation of cancer. 



We believe that our investigations which were carried 

 out with the cooperation of Miss Lathrop established the 

 importance of heredity in the etiology of cancer beyond 

 doubt, and they point more accurately to the mode of in- 

 heritance and the interaction between heredity and other 

 factors (7). Subsequently Miss Maud Slye began to 

 use a lai-ge stock of mice wliieli she had collected for 

 l)iologic;il piirpo>,-s f.-r n siniih.r slndv uf hcmlity of 

 cancel' ill mice (S). While in uciicral her (-(.iiehisions 

 as t.) tlir si.milticaiirr of heredity in cancer agree with 

 oiirs and are thus confirmatory of ours, she has extended 

 her rex 'a relies in \ arious other w^ays and has made val- 

 ual)h' coiit riluit ioii>. In regard to certain questions our 

 conchisions differ. To tliose we shall have occasion to 

 refer in the foMowing pa.uvs. 



The foHowinu' i> a >nniiiiar> of our main conclusions: 

 1. Tlie eaneer rale of each strain of family is a definite 

 eharaeteristie of thi^ >traiii and i> t ransmit'ted bv hered- 



Wliil.' these strains represent composites, they are on 

 the whole in so far homogeneous, as in the large iiia.ioi'ity 

 <if ca^e^ -ui)sti'ains showed similar tumor rates. Tims in 



the ea^' of the iMiglisli and (^vam, for instance, numer- 

 ous Mih>trains sin. wed the typical tumor rat.'S. In a 

 number of cases indi\ idual families were separated and 

 followed, and on the wh(»le their tumor rate agreed very 



