ON THE PHYSIQUE AND ABILITY OF OFFSPRING 5 



visited the homes. There is little doubt that the investiga- 

 tion in Manchester, and the records provided for us by 

 Miss Mary Dendy, were of precisely the same character 

 and as reliable as the Edinburgh Report, which even 

 Professor Marshall allows to be of ' marvellous excellence '. 

 It is not possible to dismiss the confirmatory evidence of 

 the Manchester material in the light manner adopted by 

 the Cambridge economists. 



At this point I may stop to illustrate what I term their 

 faulty logic when they approach a statistical question. 

 Mr. Keynes draws attention to the fact which he says is 

 'not explicitly stated ' in our memoir,^ that 24% (actually 

 27 %) of the fathers, and 14 % of the mothers of the feeble- 

 minded were classed as alcoholic. "At Nottingham," he 

 tells us, " where the families of 300 feeble-minded children 

 were investigated, 25 % of these families were found to 

 be alcoholic. But as the proportion of alcoholic families 

 in the population at large cannot be as high as 25 %, the 

 evidence suggests a connexion between feeble-mindedness 

 and alcoholism, rather than the contrary " (p. 770). It 

 is needful here to note the reasoning process ! The 

 percentage of alcoholic among the parents of the feeble- 

 minded is stated — no attempt is made to measure the 

 amount of alcoholism in the parents of the non-feeble- 

 minded of the same class, but a vague assertion made 

 that it cannot be as high in the population at large ! The 

 only way to answer such a question is to actually deter- 

 mine the amount of alcoholism in a sample of the popu- 

 lation similar to that from which these feeble-minded 

 children were drawn. These children were those of the 

 working classes, who alone a.re sent to the special schools. 



' The actual numbers, of far more value than percentages, are given 

 on p. 3S. 



