STUDIES IN THE SEX-RATIO IN MAN. 259 



SECONDARY SEX-RATIO. 



The sex-ratio of the living-born is, on a rough average for all 

 European countries, 105-106; but this number may vary mark- 

 edly even in comprehensive statistics. Manifold explanations 

 for these variations have been offered and these will be considered 

 briefly farther on. In the individual countries small differences 

 in the secondary sex-ratio may exist, as shown in the following 

 examples taken from a table by Ploss: 



Russian Poland 101 Denmark 105 



England and Ireland 104 European Russia 105 



France 105 Italy 106 



Germany 105 Austria 106 



Switzerland 105 -Massachusetts 106 



Belgium 105 Spain 107 



Holland 105 Connecticut no 



Sweden 105 



Concerning countries outside of Europe there is little information. 

 Newcomb ( '04) states that in Japan the excess of males in more 

 than a million births was practically the same as in European 

 countries. According to the same author, it seems probable 

 that among the negroes of the United States there is a slight 

 excess of female births. 



As a result of the unequal mortality of the sexes the secondary 

 sex-ratio becomes reversed early in life. Kroon ('17) states that 

 in Holland the sex-ratio of mortality during the first year of life 

 is 119; that is, the mortality among male infants is one fifth again 

 as great as among females. He also states that during the first 

 two months of life this ratio reaches even 139. Analogous num- 

 bers for the first year of life are given by Prinzing ( '06) : 



Italy in England 121 



Rumania 115 Sweden 121 



France 119 Denmark 121 



Austria 119 Norway 1 23 



Switzerland 120 



Kroon 's statistics show that this high sex-ratio of mortality of 

 the first year soon decreases, reaching its minimum approxi- 

 mately 80 between the fourteenth and fifteenth year. Ac- 

 cording to Prinzing ( '05) the mortality from the ages of 5 to 20 

 years is greater in females, and indeed in the latter part of this 



