STUDIES IN THE SEX-RATIO IN MAN. 



ADOLF H. SCHULTZ, 

 CARNEGIE INSTITUTION OF WASHINGTON. 



The numerical proportion of the sexes has always been a sub- 

 ject of great interest. The question whether they occur with 

 equal frequency in man bears a close relation to the problem of 

 sex-determination and comparative sex mortality. While the 

 original sex-ratio is conditioned upon sex-determination, mor- 

 tality may in the course of time change it. It will be shown that 

 sex-ratio is not constant but varies in the different periods of life 

 and under manifold influences. Most of the information at 

 hand in regard to sex-ratio is derived from statistics of new-born 

 and adults, but as regards intra-uterine life as far back as con- 

 ception, our knowledge on the subject is limited to a few conflic- 

 ting estimates. One of the purposes of this paper is to elucidate 

 as far as possible this last problem. Inasmuch as the supposition 

 that sex is determined before or at the time of fertilization is 

 generally accepted, one may speak of a sex-ratio of conceptions, 

 which may also be called original, physiological, or primary sex- 

 ratio. That at birth, therefore, should be termed secondary 

 and finally the sex-ratio of adults, tertiary. 



TERTIARY SEX-RATIO. 



The consideration of sex-ratio in adults will be limited to 

 general remarks. With only a few exceptions European countries 

 have a greater proportion of women than men. According to 

 Rauber ('oo) the sex-ratio 1 including all ages, for all Europe, is 

 97.8; for Asia 104.6; for Africa 103.3; f r America 102.2, and for 

 Australasia 114.3. According to Brooks ('87) the Australasian 

 colonies had in 1881 a sex-ratio of 143.72 for the aborigines, and 

 one of 118.64 for the population of foreign descent. However 



1 The most common method in use for representing the average sex-ratio is to 

 determine a number which indicates the proportion of males to every hundred 

 females. Unless otherwise stated, this is the method herein used. The sex-ratio 

 is also frequently called masculinity. 



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