G ALTON AND STATISTICAL STUDY OF INHERITANCE 1 73 



marriages no children are reported, while from three other families 

 no report is made except that all the children hear, so that the 

 8ii children which are reported are from only 304 families, and 

 in many of these only one parent was deaf. Of the loi children 

 of 40 of these marriages none are reported as deaf, and all but 

 II are reported as hearing, and the 710 children are from the 

 remaining 264 marriages. In 52 of the marriages both father and 

 mother were congenitally deaf, and these are the parents of 48 

 out of the 104 congenitally deaf children, but they are the parents 

 of only 151 of the total number of 811 children, and nearly 32 

 per cent of all the children of these congenitally deaf parents 

 are congenitally deaf. 



In two of the groups in which the marriages may be classified 

 the number of marriages and the number of children are about 

 equal, but there is a most remarkable difference in the number of 

 deaf children. 



In 55 marriages, with 139 children, both parents are reported 

 as adventitiously deaf, while in 52 marriages, with 151 children, 

 both were congenitally deaf. In the latter group, 52 children, or 

 31.78 per cent, are congenitally deaf, only 88 are stated to hear, 

 and no facts are given about the hearing of 15 of them. In the 

 first group only 4 of the 139 children, or 3.87 per cent, are re- 

 ported as congenitally deaf, 129 are reported as hearing, and 6 are 

 not reported. 



I have divided all the marriages into four groups : In one 

 all the children hear; in the second 5 to 6 per cent are deaf; 

 in the third from 12 to 18 per cent are deaf; and in the fourth 

 31.78 per cent are deaf. In the first group, in which all the 

 children hear, 5 of the marriages, with 18 children, are be- 

 tween a hearing husband and a wife who is adventitiously deaf; 

 I marriage, with 4 children, between a hearing man and a woman 

 the source of whose deafness is not stated; 6 marriages, with 13 

 children, where wife hears and husband is adventitiously deaf ; 

 23 marriages, with 51 children, where husband is adventitiously 

 deaf, and wife deaf from unknown causes; 2 marriages, with 6 

 children, where both were deaf from unknown causes; i marriage, 

 with 4 children, where husband is deaf from unknown causes and 

 wife hears ; and 2 marriages, with 5 children, where wife is con- 



