f relatives; while the
respective proportions when the parents are not cousins are 25.5 per
cent and 40.7 per cent--in the one case less than half, and in the other
two-thirds, as great.

Further statistics bear out the findings of the census. Dr. E. A. Fay in
his "Marriages of the Deaf"[44]--a work we are soon to notice--finds
that, though consanguineous marriages form only about one per cent of
the total number considered, 30.0 per cent of the children of deaf
parents who are cousins are deaf, and that 45.1 per cent of such
marriages result in deaf offspring; but that when the parents are not
cousins, the respective proportions are 8.3 per cent and 9.3 per
cent--only about a fourth and a fifth as great. In the Colorado School,
out of 567 pupils in attendance from the beginning to 1912, in 17, or 3
per cent, the parents were related before marriage. In the Kentucky
School, out of 83 pupils admitted in 1910 and 1911, 18, or 19.3 per
cent, and out of 42 admitted in 1912 and 1913, 8, or 19 per cent, were
the offspring of parents who were cousins. In the Iowa School, out of 62
admissions in 1911 and 1912, 4, or 6.5 per cent, and in the Maryland
School, out of a total attendance in 1911 of 135, 13, or 9.2 per cent,
had parents who were cousins.[45]

Consanguineous marriages, so far as the effect on deafness is concerned,
are not of relatively frequent occurrence. But where they do take place,
there is found a decided connection between them and deafness, the
increased tendency thus to transmit a physical abnormality being plain.
How far, however, if at all, such deafness is to be directly ascribed to
consanguineous marriages, is a matter for question. The main
consideration seems to be that in such marriages the chances are at
least doubled of the offspring acquiring the characteristics of the
parents; and that in them the liability is thus proportionately enhanced
of transmitting deafness.[46]

THE DEAF HAVING DEAF RELATIVES

We are now to examine what traces there may be of deafness in a family
by noting what proportion of the deaf have deaf relatives, and are to
attempt to see what may be its bearings upon the question of heredity.
In the census investigations,[47] we find that out of 34,780 deaf
persons who answered, there are 10,033, or 28.8 per cent, who have deaf
relatives of some kind, direct or collateral, 8,170, or 23.5 per cent,
having deaf brothers, sisters or ancestors. In all of these we can
without dif