468 
Hereditarii Deafness 
relatives is sometimes used to assist classification into the congenital and acquired 
classes, it follows that those who are included in the former class cannot be used 
as a fair sample of true congenital deaf-mutes for the purpose of the study of the 
inheritance of deafness. 
Methods and Results. 
(1) Correlation between Father and Children and Mother and Children. 
The first step taken was to tabulate afresh the offspring born from the various 
classes of marriages enumerated below, in doing which I have only used such 
families as had their total number of offspring definitely stated. Table I. shows 
TABLE I. 
Showing number of marriages and number of deaf and hearing offspring produced from, 
them, in which either the father or the mother or both parents were deaf. 
Number of Children 
Class of Marriage 
Number of 
Marriages 
Deaf 
Hearing 
Doubtful 
1 Father born deaf, Mother born deaf 
311 
184 
480 
46 
2 Father born deaf, ]\Iother not born deaf 
552 
93 
1078 
84 
3 Mother born deaf, Father not born deaf 
562 
96 
936 
86 
4 Father deaf but not known to be born deaf. Mother ditto 
1142 
68 
1696 
217 
5 Father deaf but not Ivuown to be born deaf. Mother born deaf 
478 
72 
767 
82 
6 Mother deaf but not known to be born deaf, Fatlier born deaf 
442 
66 
831 
70 
7 Father deaf but not known to be born deaf, Mother not deaf 
234 
47 
449 
21 
8 Mother deaf but not known to lie born deaf, Fatlicr not deaf 
153 
15 
292 
18 
9 Total of marriage.s in which Father was deaf ... 
2717 
464 
4470 
450 
10 Total of marriages in which Mother was deaf ... 
2610 
429 
4235 
437 
the result of this process. The first class of marriage consists of those in which 
both the husband and wife (the father and mother of the family) were stated to be 
congenitally deaf. The second consists of those in which the husband was con- 
genitally deaf but the wife was either adventitiously deaf, not deaf at all, or where 
doubt existed as to nature of her deafness, or as to whether she was deaf or not. 
Class 3 is the converse of this. In class 4 both the husband and wife were deaf, 
but they were either adventitiously deaf or at any rate were not certainly known 
to be congenitally deaf Class 5 : the husband's deafness was similar in nature to 
that of class 4, but the wife was born deaf, and class 6 is the converse of class 5. 
In classes 7 and 8 the husband in the former, and the wife in the latter, were deaf 
in the same manner as those in class 4, while the wife in the first case, and the 
husband in the last, were not deaf at all. Class 9 sums up all the cases in which 
the husband was deaf at all, and class 10 does the same for the wives. 
It is interesting to note the high proportion (•2771 of the number about whom 
it was known whether they were deaf or hearing) of deaf children in class 1 
