308 



THE AMERICAN NATURALIST 



[\'oL. XLI 



A considerable increase in the sexual ratio occurs when still 

 births are included. The sexual ratio for the city of Chicago, 

 based upon all births reported in the years 1898 to 1902 inclusive, 

 (141,233), is 1065. During this period 4828 males and 3554 

 females were prematurely or still-born. If these premature and 

 still-births are deducted from the total number reported, the 

 number of males to 1000 females is 1035. It becomes necessary, 

 then, to decide whether or not still-births shall be counted. Still- 

 births must be reported under penalty. Since the living children 

 are the ones voluntarily reported, their record is not complete; 

 but we may suppose that the parents are as apt to report a birth 

 of one sex as of the other. The statistics of living births, there- 

 fore, in localities where birth registration is not compulsory, 

 probably approach more nearly to the true ratio than the ratio 

 based upon both still- and living births. If birth registration is 

 compulsory, the ratio should be computed on a basis of all births 

 reported. The ratio for Chicago computed on the basis of living 

 births only is very nearly the same as the ratio for England. The 

 ratio for Massachusetts, computed from living births only, is less 

 than that based upon both living and still births. It is probable, 

 therefore, that the incompleteness of the statistics is the most 

 serious source of error. 



The constancy of the sexual ratio.— An examination of the sta- 

 tistics shows a remarkable constancy of the sexual ratio in all 

 parts of Europe and in the United States, for a period ranging 

 from 1856 in Massachusetts, through 1871-1880 in the German 

 Empire, to the year 1902 in Chicago. During these years and in 

 the various countries, there were periods of war and peace, of 

 famine and plenty, beside a great variety of racial and climatic 

 conditions. Yet the greatest variation from the mean, exclusive 

 of England, is only eleven in 1000 — a difference of one per cent. 



In the same country for a period of years, the ratio is approxi- 

 mately constant. As an example, we may take the statistics for 

 England (Tal)le III) during the twelve years from 1888 to 1899, 

 inclusive. 



