EMBRYOLOGY AND HUMAN MORTALITY 139 



step further back and combine them under the headings 

 of the primary germ layers from which the several organs 

 developed embryologieally. To do this was a task of 

 considerable diflBculty. It raised intricate, and in some 



TABLE 12 



Showing the relative influence of the "primary germ layers in human mortality 

 (Items 64 and 65 charged to ectoderm) 



TABLE 13 



Showing the relative influence of the primary germ layers in human mortality 



(Items 64 and 65 charged to mesoderm) 



cases still unsettled, questions of embryology. Further- 

 more, the original statistical rubrics under which the data 

 are compiled by registrars of vital statistics were never 

 planned with such an object as this in mind. Still the thing 

 seemed worth trying because of the biological interest 

 which would attach to the result, even though it were some- 



