38 THE FALL OF THE BIRTH-RATE 



of field-mice, or plagues of locusts. On this hypo- 

 thesis (loc. cit. p. 22) " the birth-rate is not dependent 

 in general on the immediate conditions which sur- 

 round the organism, but upon conditions which prob- 

 ably precede the period of high birth-rate and which 

 are favourable to the storage of the specific energy." 

 We know nothing whatever of the causes which lead 

 to such "epidemics" of an infective organism or of 

 higher animal forms: we only know that they do 

 occur, and there is no reason why man should be 

 exempt from analogous phenomena. Dr Brownlee 

 endeavours to relate periods of rapid increase in 

 nations with other symptoms of energy, e.g. of re- 

 markable literary output and of "racial adventure." 

 I must refer to his original paper for the detailed 

 argument, and to his evidence before the Birth-rate 

 Commission where the hypothesis was supported by 

 Dr Chalmers. 



At the end of his paper Dr Brownlee states that, in 

 advancing such a hypothesis, he does not mean to 

 discount the direct influence of environment in pro- 

 ducing an increase of population, but apparently he 

 would regard any such effect as in general subsidiary. 

 In my own investigation of 1905, however, I endeav- 

 oured to trace the effect of definite causes on the birth- 

 rate. First of all I endeavoured to see if there was 

 any direct response to the economic wave the short- 

 period movement usually some 7 to n years from 

 crest to crest which is so marked a feature in the 

 course of trade, or of prices, or of almost any index to 

 economic activity. The problem is not an easy one, 

 for we have first to estimate the indirect effect owing 

 to the influence of the economic wave on the marriage 

 rate. Calculations showed that the actual oscillations 

 in the birth-rate were nearly twice as large as they 

 would be if they were merely the indirect effect of 



