ese states the number being over 400 per
million. Why there should be these differences in the respective
proportions of the deaf in the population of the several states, we
cannot say; and we are generally unable to determine to what the
variations are to be ascribed--whether they are to be set down to
particular conditions of morbidity, the intensity of congenital
deafness, or other influences operating in different sections; or,
perhaps in some measure, to the greater thoroughness with which the
census was taken in some places than in others.

AGE WHEN DEAFNESS OCCURRED

The vast majority of the deaf lost their hearing in early life, and most
of them in the tender years of infancy and childhood. More than ninety
per cent (90.6, according to the returns of the census) became deaf
before the twentieth year; nearly three-fourths (73.7 per cent) under
five; over half (52.4 per cent) under two; and over a third (35.5 per
cent) were born deaf. Deafness thus occurs in a strongly diminishing
ratio with advancing years.[6] These facts may be indicated by the
following table,[7] which shows the percentages of those who became deaf
at different ages.

THE DEAF ACCORDING TO AGE OF OCCURRENCE OF DEAFNESS

At birth 35.5
After birth and under two 16.9

Under two years 52.4
2 and under 4 17.1
4 and under 6 7.3
6 and under 8 4.5
8 and under 10 2.8
10 and under 12 1.8
12 and under 14 1.6
14 and under 16 1.3
16 and under 18 1.0
18 and under 20 0.8

Under five 73.7
5 and under 10 10.5
10 and under 15 4.0
15 and under 20 2.4

Under 20 90.6
20 and under 40 5.7
40 and under 60 2.4
60 and under 80 1.1
80 and over 0.2

ABILITY OF THE DEAF TO SPEAK

We have just seen that "dumbness" frequently follows upon deafness, or
that it is usually believed to be an effect of deafne