470 
Hereditarii Deafnesi^ 
whether they were deaf or hearing. There is no reason to suppose that among 
the doubtful ones the deaf did not bear the same proportion to the hearing as 
among the others ; that is to say that among 450 of them there would be 42 deaf 
and 408 hearing ; therefore by adding these to the others we have 506 deaf and 
4878 hearing. Weighting the fathers with the number of their children 
(i.e. including them once for each child that they have), there are then 4878 
deaf fathers with hearing children, and 50G with deaf In order to complete the 
table it is necessary to know how many hearing fathers with hearing children, and 
how many with deaf children, would occur in a random sample of the population 
containing the deaf fathers mentioned above. Now from Table II. we know that 
a total of 3658 deaf people have in 132 cases deaf fathers, and in the remaining 
3519 cases hearing fathers ; and we have to include in the table we are con- 
structing 506 deaf people with deaf fathers, therefore we may take it that the 
number of deaf people with hearing fathers which correspond with this number is 
506/132 multiplied by 3519, which is equal to 13,489. 
There only remains in order to complete the table to determine how many 
hearing people with hearing fathers should be included in the sample. We know 
from the American census of 1890 that 659 deaf people occur in every million of 
the general population. We are dealing here with 506 plus 4878 = 5384 deaf 
fathers, therefore if we assume that deaf fathers bear the same numerical relation 
to hearing fathers, as deaf persons in general bear to hearing persons, then the 
5384 deaf fathers occur among a total number of 5384/659 multiplied by a million, 
which is equal to 8,169,954 fathers, and as 5384 of these are deaf there remain 
8,164,570 who are hearing. Of these 13,489 have deaf offspring, therefore 
8,151,081 have hearing offspring, and thus Table III. may be completed. 
TABLE III. 
Fathers. 
CD 
IS 
O 
Deaf 
Hearing 
Hearing 
Deaf 
4878 
50G 
8,151,959 
13,489 
1 
/* = 2 -926730 
//= -005507 
k =3-212070 
A'= -002294 
r = -51 
TABLE IV. 
Fathers. 
Deaf 
Hearing 
Hearing 
Deaf 
4878 
506 
21,222,727 
13,489 
h =3-477260 
H= -000945 
I- =3-212070 
K= -002294 
r = -57 
There is also another way of completing the table. If instead of assuming that 
deaf fathei's bear the same numerical relation to hearing fathers, as deaf persons in 
