fifty-one children, where husband is adventitiously deaf and wife deaf from unknown causes; two marriages, with six children, where both were deaf from unknown causes; one marriage, with four children, where husband is deaf from unknown causes and wife hears; and two marriages, with five children, where wife is congenitally deaf and husband deaf from unknown causes. None of the 101 children of these forty marriages are reported as deaf.
In the second group, where from five to six per cent of the children are deaf, eighty-seven are the children of thirty-seven marriages where the husband was congenitally and the wife adventitiously deaf; and 139 are the children of fifty-five marriages where both husband and wife were adventitiously deaf.
In the third class, where from twelve to eighteen per cent of the children are congenitally deaf, 124 are children of fifty-one marriages where husband was adventitiously and wife congenitally deaf; sixty-six were children of sixteen marriages of hearing husband and congenitally deaf wife; seventy-two were children of twenty-six marriages where wife hears and husband is congenitally deaf; and seventy-one of twenty-nine marriages of congenitally deaf husband with deaf wife of unknown origin. In all the families of this group one parent was congenitally deaf.
In the fourth class, where 31·78 per cent of the children are congenitally deaf, all the parents in the fifty-two marriages with one hundred and fifty-one children are congenitally deaf.
While too few to give quantitative results, these statistics prove that it is the congenital and not the adventitious deafness which is transmitted.
Of the fifty-two families in which both parents are congenitally deaf, twenty-three have congenitally deaf children.
Of the thirty-seven families in which the husbands are congenitally deaf and the wives adventitiously deaf, two have deaf children—four in one family and one in the other.
Of the fifty-one families in which the fathers were adventitiously deaf and the mothers congenitally deaf, seven produced deaf children, and nine of the congenitally deaf children came from two families.
There are fifty-five families in which both parents are adventitiously deaf, and from these have sprung four congenitally deaf children—one in each of four families.
Four of the sixteen families in which the husbands hear and the wives are congenitally deaf have deaf children.
In five families out of the twenty-six in which the husbands are congenitally deaf and the wives hear, there are children born deaf.
Six of the twenty-seven families in which the husbands were
