SOCIAL AND WORLD ASPECTS 237 



look for a higher racial type from the indiscriminate 

 blending of such elements appears to be the height 

 of folly. 



All general problems of race and movements of 

 population are closely connected with questions of 

 birth- and death-rates. In an able analysis of the 

 causes of death in man from an evolutionary and 

 embryological point of view, Pearl (1920) has shown, 

 from statistics of the United States, England, and 

 South Brazil, that man's greatest enemy is his own 

 endoderm. In the two former countries about 

 57 per cent, of all deaths which are biologically 

 classifiable result from breakdown and failure to 

 function of organs derived from the endoderm in their 

 embryological development. Only 8 to 13 per cent, 

 of deaths result from breakdown of ectodermal 

 organs, the remaining 30 to 35 per cent, being ascribed 

 to organs of mesodermal origin. The endoderm has 

 been least differentiated in evolution, and hence is 

 least adapted to resist the vicissitudes of environment. 

 Sanitary and public health measures are largely 

 directed to softening the asperities of the environment, 

 so that the relatively inefticient and primitive endo- 

 derm can cope with it. Organologically considered, 

 the respiratory and alimentary systems are most 

 largely responsible for human deaths. Then follow 

 in order the circulatorv and nervous svstems, the 

 kidneys, sex organs, skeletal and muscular S3'stem, 

 the skin, and finalty the endocrinal system or glands 

 of internal secretion. Differences in the efficiency, 

 structure, and functioning or tendency to disease in 

 all of these groups of organs no doubt exist and are 

 inherited. In this way the factor of heredity directly 

 affects the death-rate in families, and is often an 

 important element in determining the age at which 

 death will take place. 



It is now well known from the statistical records of 



