SEX-INCIDENCE IN ABORTIONS. 



179 



SECONDARY SEX-RATIO. 



The sex-ratio of the living-born for all European countries is, roughly averaged, 

 105 to 106, but this may vary markedly even in comprehensive statistics. Mani- 

 fold explanations for these variations have been offered and these will be con- 

 sidered briefly farther on. In the individual countries small differences in the 

 secondary sex-ratio may exist, as shown by table E, taken from a table by Ploss. 



We have very little data concerning the sex-ratio of new-born among races 

 other than white. Newcomb (1904) states that in Japan the excess of males in 

 over 1,000,000 births was practically the same as in European countries. Accord- 

 ing to the same author, it seems probable that among the negroes of the United 

 States there is a slight excess of female births. In a table by Nichols (1907) one 

 finds the following sex-ratios among the living-born of primitive races: Japan 

 (1877-1902), 104.7; India (1891-1900), 107.5; negroes of United States (1900), 

 99.8; and an average since 1880 of 100.9. 



TABLE E. Secondary sex-ratio. (From Ploss.) 



TABLE F. Sex-ratio of mortality during first year of life. 

 (From Prinzing.) 



As a result of the unequal mortality of the sexes, this secondary sex-ratio 

 becomes reversed early in life. Kroon (1917) 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 greater by one-fifth than among females; also, that during the first two 

 months of life this ratio reaches even 139. Analogous numbers for the first year 

 of life are given in table F (Prinzing, 1906). 



Kroon's statistics show that this high ratio of mortality of the first year of 

 life soon undergoes a decrease, reaching its minimum (approximately 80) between 

 the fourteenth and fifteenth year. According to Prinzing (1905), and also Willcox 

 (1904), the mortality from the ages of 5 to 20 years is greater in females, and indeed 

 in the latter part of this period it is the result chiefly of tuberculosis, for which 

 disease the common occurrence of anaemic and chlorotic conditions at the time of 

 puberty furnishes an excellent soil. After this age the sex-ratio of mortality in- 

 creases rapidly and results in the reversion from an excess of males to an excess of 

 females, and the higher the death-rate the earlier will this reversion take place, 

 the death-rate being influenced by various factors. It can be said, for instance, 

 that as a general rule the death-rate of infants is especially high in countries with 

 a high birth-rate, such as Russia and China. This, in connection with the high 

 sex-ratio of infantile mortality, will tend to decrease very rapidly the sex-ratio of 

 the surviving infants. 



