470 



Prof. K. Pearson. 



[June 4, 



deaths in these age-groups for the same years were dealt with, and (b) no 

 allowance whatever was made for the differential environment of the 

 administrative counties, it is difficult to find any real bearing of the data on 

 the problem of natural selection in man. 



The only method by which data for different districts can be compared is 

 by endeavouring to fix the nature of the environment. We want to know 

 whether under a constant environment the correlation between the death- 

 rates of infancy and of childhood is positive or negative. Dr. E. C. Snow,* 

 working on both English and Prussian data, finds, using a variety of criteria 

 of sameness of environment, that when this factor is allowed for the 

 correlation between infantile and child death-rate is negative, and sub- 

 stantially negative. In other words, within the same group under the same 

 environment, the greater the infantile death-rate, the less is the death-rate 

 among the survivors ; that is to say, the physically stronger members of the 

 group are those which survive the ordeal. 



Dr. Arthur Newsholme in his recent paper, " National Importance of Child 

 Mortality,"! has asked the question (p. 332) : — " Is it certain that a lower 

 infant mortality will produce a survival of an increased proportion of 

 physically inferior children ? " and he reaches the conclusion that : — "A high 

 -infant death-rate in a given community implies in general a high death-rate 

 in the next four years of life, while low death-rates at both age-periods are 

 similarly associated " (p. 334). " So far from any weeding out of the weaklings 

 'being manifest, the counties with a high infant mortality have a death-rate 

 which is relatively higher still in the next four years of life." As evidence 

 for this he cites the correlation between infantile and child death-rates for 

 the same period, and the life- tables for Healthy Districts and for all England 

 and Wales. These life-tables, however, show, as I indicate below, that a 

 heavier infantile mortality has actually a lower child mortality associated 

 with it. It appears to me that the non-allowance for differential environment 

 renders Dr. Newsholme's reasoning insecure. 



It is not generally realised that the infantile mortality in England and 

 Wales has not been falling but steadily rising since the restriction in size of 

 families. On the other hand, the child mortality has been steadily falling. 

 The numbers provided by the Eegistrar-General's Life-Tables^ are : — 



* "The Intensity of Natural Selection in Man," 'Drapers' Company Eesearch 

 Memoirs,' Dulau & Co., 1911. 



t ' Journal of the Eoyal Sanitary Institute,' 1910, vol. 31, p. 334. 



X ' Supplement to the 65th Annual Eeport,' 1891—1900, Part I, pp. xlviii— L London, 

 1907. 



