viii] HEREDITY 101 



mental character in man. It forms... probably no 

 exception to an orderly system of inheritance in 

 man, whereby on the average about one-half of the 

 mean parental character, whether physical, mental or 

 pathological, will be found in the child. It is accord- 

 ingly highly probable that it is in the same manner 

 as other physical characters capable of selection or 

 elimination by unwise or prudential mating in the 

 course of two or three generations.' (Heron [10]). 

 Similarly for congenital deafness, Schuster writes 

 '...that striking confirmation has been obtained of 

 previous work on widely different characters, at any 

 rate with regard to the correlation between father 

 and children, and mother and children.' [31]. 



These examples, which might be added to, of 

 results obtained by 'biometric' methods, make it 

 sufficiently clear that a knowledge of the facts of 

 inheritance is of importance to mankind, and that 

 the further collection of accurate data is one of the 

 most needed social requirements. Before passing on 

 to other aspects of the question one other subject 

 may be mentioned. The measure of resemblance 

 in these characters has not only been worked out 

 between parent and child, but between brothers 

 and sisters, between children and grandparents and 

 uncles and aunts, and between cousins. Some esti- 

 mate can therefore be made of the probability of an 

 individual being affected if his relatives are known, 



