188 THE LAW OF BIRTHS AND DEATHS 



to be authentic, it would seem that the power wires pro- 

 duced an electrically charged atmosphere in the immediate 

 neighbourhood, and this may have affected the reproductive 

 powers through the nervous systems of the sheep. Perhaps 

 it had an enervating effect similar to that produced by 

 the electrical condition of the atmosphere which precedes 

 a thunderstorm. 



In addition to a careful study of the effect of all the 

 nutritive factors of the environment upon fertility, we 

 need a systematic inquiry into the effects of intellectual 

 activity. A good deal of striking evidence has already 

 been given, but we need much more far-reaching and 

 systematic inquiries than have yet been carried out. 

 Obviously the proportion of completely sterile marriages 

 offers the best test both for this and for the general question 

 whether there has been a great decline of fertility due to 

 natural causes. Thus far there have been no adequate 

 statistical inquiries directed to this end. Some signifi- 

 cant facts have been given earlier in this work. More 

 figures are given in the Report of the National Birthrate 

 Commission, but they are scrappy and not arranged to 

 throw any real light on the relative proportion of com- 

 pletely sterile marriages in comparisons between different 

 countries, different periods and different social classes, 

 which is the kind of information needed. For example, 

 " sterility is much more frequent among American women 

 than among foreign women in America. Among various 

 groups in Boston, St. Louis and elsewhere, it varies 

 between 20 and 23 per cent., and in some smaller groups 

 is even considerably higher, while among foreign women 

 it is only 13 per cent." l It may be added that the 

 average fertility of native American women is considerably 

 less than that of foreign-born women. Malthus quotes 



1 The Task of Social Hygiene , Havelock Ellis, p. 173. 



