but
with the present data a further analysis has no significance.[91]

[Footnote 91: Mr. Edgar Schuster (_Biometrika_, vol. iv, p. 465) finds
from Dr. Fay's statistics that the average parental correlation
(parent and child) of deafness is: paternal, .54; maternal, .535.
English statistics of deafness give: paternal correlation, .515;
maternal, .535. The fraternal correlation from the American data is
.74 and from the English .70. See _infra_, p. 92.]

If, then, consanguineous marriages where relatives are deaf have a
greater probability of producing deaf offspring, and also a greater
probability of producing plural deaf offspring, than ordinary
marriages, and two thirds of the congenitally deaf offspring of
consanguineous marriages do have deaf relatives, it does not seem
necessary to look beyond the law of heredity for an explanation of the
high percentage of the congenitally deaf who are of consanguineous
parentage.

In those cases of deafness which, in the Census returns, are ascribed
to specific causes, the factor of consanguinity is still noticeable,
although the percentage of the non-congenitally deaf who are the
offspring of cousins never exceeds 5.3 (Table XXVIII). But the
influence of heredity is not removed by the elimination of the
congenitally deaf. Many instances are known where successive
generations in the same family have developed deafness in adult life,
often at about the same age and from no apparent cause. The following
case well illustrates this point. It is furnished me by a
correspondent in whom I have great confidence. The facts are these:
A---- aged 28 married B---- aged 19, his first cousin who bore the
same surname as himself. Both lived to old age and were the parents of
eight children, two of whom died in infancy. My informant further
states:

Having personally known very well all of the surviving six
children of this family, I can truthfully state that all were
unusually strong, active and vigorous people and all the
parents of healthy children. A---- was troubled with deafness
as long as I can remember, and this physical trait he
transmitted to all of his children, though some of them did not
develop the same till well along in life. C---- (the youngest
son), however, began to indicate deafness quite early. No one
of his four children is in the least deaf.

It will be noticed here that whereas in the case of the cousin
marriage the trait was so