CHAPTER VI. 



SEX-INCIDENCE IN ABORTIONS. 

 BY ADOLPH H. SCHULTZ. 



The numerical proportion of the sexes has always been a subject of great 

 interest. The question whether man produces males and females in equal or un- 

 equal numbers bears a close relation to the problem of sex determination and must 

 be studied in connection with the death-rate in different periods of life and the 

 comparative sex-mortality. While sex-ratio is conditioned originally upon sex- 

 determination, mortality may change it in the course of time. It will be shown 

 herein that sex-ratio is not constant, but varies in the different periods of life and 

 under manifold influences. Most of the information at hand concerning it is 

 derived from statistics of the new-born and adult, but as regards intrauterine life, 

 as far back as conception, our knowledge is limited to a few incomplete statistics 

 and conflicting estimates. The main purpose of this study is to elucidate as far 

 as possible this problem of the proportion of the sexes in utero, both living and 

 aborted. The short review of the sex-ratio after birth, given herein, is intended to 

 show the fluctuations in the numerical proportion of the sexes throughout life and 

 may serve for a comparison of the relative mortality before and after birth. The 

 last part of the study is a compilation from the literature of factors which may 

 possibly have an influence on the original sex-ratio and of conditions which may 

 change it during the course of prenatal life. 



In view of the generally accepted supposition that sex is determined either 

 before or at the time of fertilization, one may speak of a sex-ratio at conception 

 or a sex-ratio of fertilized ova. This may also be called an original, physiological, 

 or primary sex-ratio; the sex-ratio of the new-born may be termed secondary 

 and, finally, that of adults is the tertiary sex-ratio. The latter term, in contrast to 

 the preceding ones, does not apply to a definite time, such as conception or 

 birth, but may be used collectively to designate the changing numerical proportion 

 of the sexes after they reach maturity. 



TERTIARY SEX-RATIO. 



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

 ing to BUcher (1892), for Europe the sex-ratio, 1 including all ages, is 97.6; for 

 Asia 104.5; for Africa 103.3; for America 102.8; for Australia 117.4. However 

 imperfect these computations may be, they nevertheless show that Europe, with 

 its excess of females, occupies a unique position. There are only a few European 

 countries with a greater proportion of men than women. Among the American 

 negroes there is an excess of females, and among the American Indians an excess 

 of males (Cummings, 1918). According to Brooks (1887), the Australasian colonies 



1 The most common method in use for representing the sex-ratio is to determine a number which indicates the pro- 

 portion of males to every 100 females. Unless otherwise stated, this ia the method used herein. The sex-ratio is also fre- 

 quently termed masculinity. 



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