lligent attitude of the American
people in general towards the affliction of deafness, is due largely
to the work of Dr. Alexander Graham Bell. An enumeration of Dr. Bell's
services directly, and through the agency of the Volta Bureau, in this
cause, cannot be given here. For our purpose the most important of his
contributions is embodied in the Special Report of the Twelfth Census
of the United States already referred to.

As in the investigation of the Blind, the circular letter sent to each
person reported by the enumerators as deaf contained questions in
regard to parentage and the existence of deaf relatives. It is
unfortunate that in these returns it is impossible to distinguish
between degrees of relationship, but in such an extensive compilation
it was doubtless impracticable to attempt to unravel the intricacies
of consanguinity. Judging from the returns of the Census of Ireland we
may assume that about half of the cases returned as "cousins" were
first cousins.

The replies to the inquiry as to deaf relatives were more carefully
analyzed, and were divided into four groups, which are referred to
throughout as (a), (b), (c) and (d) relatives. These groups are: (a),
deaf brothers, sisters or ancestors; (b), deaf uncles, aunts, cousins
or other relatives not (a), (c) or (d); (c), deaf children, (sons or
daughters); (d), deaf husbands or wives. Thus a large proportion of
the hereditary cases would be included in the first two categories,
(a) and (b).[88]

[Footnote 88: U.S. Census _Report on the Blind and the Deaf_, p. 127.]

The causes of deafness are given in detail, but as might be expected
the returns are not as definite or as accurate as we should desire.
The causes given have been grouped under five main heads; these again
are subdivided, often into divisions numerically too minute for real
statistical value. Table XXVIII includes the main groups and those
specific causes which number more than 3000 cases. The extreme
variation in the percentages of those who are the offspring of
consanguineous marriages cannot be attributed to mere chance. There is
clearly some fundamental connection between consanguinity and
congenital deafness if 11.8 per cent of all the congenitally deaf are
the offspring of consanguineous marriages, while of the adventitiously
deaf but 3.1 per cent are the offspring of such marriages. In fact we
are tempted to jump at the conclusion that consanguinity is in itself
a cause of deaf-mu