TABLE XXXIII.
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-------
|   Percentage having deaf children.
|---------------------------------------
Class of Deaf Relatives.   |      |Totally |Partially |Congenitally
|Total.|deaf.   |deaf.     |deaf.
---------------------------|------|--------|----------|-----

-------
(a), (b) or (d)            | 1.4  | 2.4    | 1.1      | 5.0
(d)                        | 3.2  | 3.3    | 2.6      | 6.4
No (d)                     | 1.1  | 1.4    | 1.0      | 2.5
(a) and (d)                | 6.3  | 6.7    | 4.3      | 7.8
(d), but no (a)            | 2.2  | 2.2    | 2.0      | 4.9
(a), but no (d)            | 1.4  | 2.3    | 1.3      | 2.6
No (a) or (d)              | 0.9  | 1.0    | 0.9      | 2.3
(a), (b) and (d)           | 9.5  | 9.9    | [A]      | 9.0
(a), (d), but no (b)       | 5.5  | 5.9    | 3.6      | 7.4
(b), (d), but no (a)       | 2.5  | 2.4    | [A]      | [A]
(d), but no (a) or (b)     | 2.2  | 2.2    | 2.0      | 5.2
(a), (b), but no (d)       | 1.9  | 3.1    | 1.7      | [A]
(a), but no (b) or (d)     | 1.3  | 2.1    | 1.2      | 2.8
(b), but no (a) or (d)     | 1.0  | 1.6    | 1.0      | [A]
No (a), (b) or (d)         | 0.9  | 1.0    | 0.9      | 2.6
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[A] Percentages not given where base is less than 100.

  Symbols:  (a) deaf brothers, sisters or ancestors; (b) deaf
  uncles, aunts, cousins, etc.; (d) deaf husbands or wives.

The striking feature of these percentages is the regularity with which they increase in proportion as the number of deaf relatives increases, until among the 242 persons who have (a), (b) and (d) relatives, 23 or 9.5 per cent also have (c) relatives.  A consanguineous marriage within a family tainted with deafness would have the same effect as doubling the number of deaf relatives, which as we have seen greatly increases the percentage having deaf children.

It would seem that the number of the married deaf reported as having deaf children is much too small, especially since Dr. Fay[89] produces statistics of 4471 marriages of the deaf of which 300 produced deaf offspring.  Counting only the 3,078 marriages of which information in regard to offspring was available these figures show an average of a little less than one such marriage in ten as productive of deaf offspring.  The total number of children of these marriages was 6,782, of which 588 were deaf.  These 3,078 marriages represented 5,199 deaf married persons as compared with the 31,334 reported in the Twelfth Census, or about one sixth.  Increasing the 300 families who had deaf children in the same ratio we have 1800 as compared with the 437 reported by the census.  But as it was inevitable that Dr. Fay’s cases should be selected somewhat, he has probably collected records of more than one sixth of all the cases where deaf children were born of deaf parents.  But we can hardly believe that he found three-fourths of such cases.  The true number therefore must be considerably greater than 437, but less than 1800.[90]