Page:Popular Science Monthly Volume 27.djvu/33

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21
CAN MAN BE MODIFIED BY SELECTION?

per cent, may have been between deaf persons, but even this is an alarming frequency, if it is true that the children of such unions are predisposed to deafness.

If it is true that our system of educating the deaf is responsible for the number of marriages between deaf persons, we should expect to find these marriages increasing in numbers, and Professor Bell has compiled from the table above quoted the following table, which shows that this is the case:

YEAR OF BIRTH. Total
recorded to have
married.
Total recorded
to have married
deaf-mutes.
Percentage.
Before 1810 129 72 55·8
1810 to 1839 715 577 80·7
1840 to 1859 233 196 84·1
1860 and after 12 11 91·7

These two tables show that the tendency of deaf-mutes to select deaf-mutes as their partners in marriage is very pronounced, and that it is much more developed now than it was during the early half of the century, and that it is steadily increasing.

Thus there is every indication that this process of selection will go on from generation to generation, and that a large proportion of the deaf children of deaf parents will themselves marry, and that, of those who marry, the majority will marry deaf-mutes.

If it is true that deafness is hereditary, this can have only one result — the increase of deafness.

There are very few reliable statistics regarding the number of children born to deaf-mutes, or the proportion of deaf children, but Dr. Turner, formerly the Principal of the American Asylum, stated, in 1868, that statistics carefully collated from records kept of deaf-mutes, as they have met in conventions at Hartford, show that in eighty-six families, with one parent a congenital deaf-mute, one tenth of the children were deaf; and in twenty-four families, with both parents congenital deaf-mutes, about one third were born deaf.

In 1854 Dr. Peet, the Principal of the New York Institution, said that, of all the families of which he had records, "about one in twenty have deaf-mute children where both parents are deaf-mutes, and about one in one hundred and thirty-five where only one is a deaf-mute; and that the brother and sister of a deaf-mute are about as liable to have deaf-mute children as the deaf-mute himself, supposing each to marry into families that have, or each into families that have not, shown a predisposition toward deaf-dumbness"

Our author has attempted to trace out from the scanty records the history of certain families in which deafness is hereditary, and he has expressed the facts in a number of graphic diagrams, two of which are here reproduced.