482 
Hereditary Deafness 
National Association, and a group of 155 families of which 64 came from the 
institution at Exeter and 91 from that at Manchester. From the 459 families 
Table XXIV. was made, and from the 155 Table XXV., both in exactly the same 
way as Table XV. 
TABLE XXIV. 
National Association in Aid of the Deaf and Dumb. 
Deaf 
Hearing 
Hearing 
Deaf 
2880 
518 
7,243,407 
2880 
h =k =3-3087 
H=K= -001674 
r = -72 
TABLE XXV. 
Exeter and Manchester. 
Deaf 
Hearing 
h =k =3-3087 
H=K= -001674 
Hearing 
727 
1,737,273 
r = -68 
Deaf 
88 
727 
The values of r were found to be '72 and '68 respectively, whereas '74 was given 
by Table XV. It may thus be said that with regard to parental and fraternal 
correlation the English material gives results which agree very well with the 
American, if one takes into consideration the roughness both of the material and 
of the methods employed. 
The mean size of the families from the National Association Register is 
6-1939 ± -0954; that of the Exeter and Manchester families is 5-1871 + -1489. 
The reason for this diffei'ence is that in the former case the families are probably 
all complete, whereas in the latter they are certainly incomplete in many cases, 
the number being taken at the time of the entry of one of their deaf members, 
generally aged 8 or 9, into one of the two institutions. 
