CAN MAN BE MODIFIED BY SELECTION? 



*9 



47 pupils had one or more parents deaf and dumb. 



38 

 29 



48 



u 



uncles or aunts deaf and dumb. 



a 



a 



a 



u 



a 







children 

 distant relatives 

 grandparents 

 1 " " " great-grandparent 



1 " " " great-uncle or aunt " 



That this is not peculiar to the pupils of this particular institution, 

 and that it holds true of deaf-mutes in general, is shown by the fol- 

 lowing table, compiled from the records of six institutions : 



The table shows that, among 5,823 deaf-mutes taken from different 

 parts of the country, 1,719, or 29^ per cent, are known to have had 

 deaf-mute relatives, and that this is due to the influence of heredity is 

 well shown when we contrast those who were born deaf with those 

 who had afterward lost their hearing. Many of those who lose their 

 hearing by accident or disease have no hereditary tendency to deaf- 

 ness, but a considerable number of those who lose their hearing at 

 some time after birth are born with an hereditary predisposition to 

 deafness. If, therefore, we contrast the congenitally deaf with those 

 who have become deaf, we should expect the latter class to have a 

 much smaller percentage of deaf relatives than the former class, but a 

 greater percentage than the community at large. 



Professor Bell has compiled the following two tables from the one 

 which is given above, and they show that, while only about 13 per 

 cent of the pupils which were not born deaf have deaf relatives, more 

 than 54 per cent of the congenitally deaf pupils are recorded as hav- 

 ing such relatives : 

 Table II. Proportion of the Non-eongenitally Deaf who have Deaf Relatives. 



