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Our main interest in the problem of adventitious deafness lies in the possible discovery whether or not it is relatively increasing or decreasing among the population, and in what respects signs appear of a diminution. We have just seen the likelihood of a decrease from certain causes; but we are to find what is indicated by statistical evidence.

To be considered first is adventitious deafness as a whole. Respecting it our only statistics are in the returns of the censuses since 1880, the different forms of deafness not being distinguished before this time. The following table will show the number of the adventitiously deaf as reported by the censuses of 1880, 1890 and 1900, with their respective percentages and ratios per million of population.[31]

NUMBER OF THE ADVENTITIOUSLY DEAF IN 1880, 1890 AND 1900

	Total Number	Adventitiously Deaf	Percentage	Ratio per Million of Population
1880	33,878	10,187	30.1	20.3
1890	40,562	16,767	41.1	26.8
1900	37,426	18,164	48.4	23.9

From this it appears that adventitious deafness is increasing in relation to total deafness, which is most likely the case, as congenital deafness, as we shall see, is evidently decreasing. Whether or not adventitious deafness is increasing in respect to the general population, the table does not disclose definitely. The statistics probably are not full enough to afford any real indication yet.

Our next inquiry is in respect to the increase or decrease of adventitious deafness from the several diseases individually, which is, upon the whole, the more satisfactory test. Here also, unfortunately, our statistics are very limited, and our findings will have to fall much short of what could be desired.

The following table, based on the returns of the censuses of 1880, 1890 and 1900, so far as the approximate identity of the several diseases can be established, will give the respective percentages found.[32]

CAUSES OF ADVENTITIOUS DEAFNESS IN 1880, 1890 AND 1900

	1880	1890	1900
Scarlet fever	7.9	11.8	11.1
Meningitis	8.4	7.8	9.6
Catarrh and catarrhal fevers	0.9	3.3	3.6[33]
Diphtheria	0.2	0.5	—[34]
Abscess and inflammation	1.0	2.5	—[35]
Measles	1.3	2.5	2.5
Whooping cough	0.5	0.8	—[34]
Malarial and typhoid fevers	1.7	1.8	3.6
Other fevers	1.1	—	2.0

In this table the most noticeable thing is perhaps the persistency with which we find most of the diseases to recur, with apparently no great change, while in certain ones, as catarrh and malarial and typhoid fevers, there seems to be rather an increase. It would be best, however, not to place very great confidence in these figures, but, so far as the census reports are concerned, to wait for more precise and uniform statistics.

We have, further, the statistics published in the reports of certain schools for the deaf. While these are perhaps not of sufficient extent to warrant full conclusions, they may be regarded as quite representative;[36] and though to be taken with something of the caution as the census figures, they may serve to throw some light upon the situation. Comparison of the proportions of pupils deaf from the several diseases at different times may be made in two ways: by finding the respective proportions over a series of successive years from a certain time back down to the present, and by contrasting the proportions in two widely separated periods, one in the present and one in the past. These will be taken up in order.

The following tables give the percentages of cases of deafness in pupils from the important diseases as found in six schools in successive years: in the New York Institution in the total annual attendance from 1899 to 1912; in the Michigan School in the total biennial attendance from 1883 to 1912; in the Pennsylvania Institution in the number of new pupils admitted quadriennially from 1843 to 1912; in the Western Pennsylvania Institution in the number admitted biennially from 1887 to 1912; in the Maryland School in the number admitted biennially from 1884 to 1911; and in the Wisconsin School in the number admitted biennially from 1880 to 1908.

I. CAUSES OF DEAFNESS IN NEW YORK INSTITUTION FROM 1899 TO 1912

	1899	1900	1901	1902	1903	1904	1905	1906	1907	1908	1909	1910	1911	1912
Total Number	466	476	481	477	464	503	508	510	543	555	565	570	546	518
Congenital	36.0	27.1	26.8	40.9	36.2	41.1	46.2	31.8	33.3	34.4	34.9	32.8	34.6	36.6
Scarlet Fever	11.4	10.1	8.9	7.1	6.5	6.9	6.5	4.9	5.3	5.0	5.7	6.1	5.7	5.0
Meningitis	9.5	9.4	7.7	7.9	7.8	7.9	11.0	12.2	16.8	18.6	17.7	17.9	19.0	19.7
Brain Trouble	10.1	9.2	8.3	8.1	7.2	5.9	5.9	7.1	9.0	8.3	8.7	8.3	8.0	8.9
Falls	9.0	7.2	5.4	4.5	3.9	4.2	3.8	5.2	5.9	6.1	6.0	5.1	5.5	5.6
Measles	5.1	3.8	3.8	2.1	3.9	4.5	4.1	4.1	4.8	4.7	4.4	4.6	0.2	0.7
Typhoid Fever	3.7	2.3	1.6	1.0	0.9	1.2	1.0	1.0	1.3	1.3	1.2	1.1	0.9	0.5
Convulsions	3.2	4.4	3.2	2.9	2.6	0.2	1.8	1.8	1.9	1.5	1.9	1.9	2.0	2.1
Various Fevers	2.5	1.5	1.4	1.0	1.7	1.6	1.6	1.6	1.5	1.3	0.7	0.5	0.5	0.7
Catarrh	2.3	2.1	1.9	1.8	1.6	1.2	1.0	2.0	1.9	1.9	1.4	0.8	1.0	0.5
Diphtheria	1.9	1.7	1.9	1.0	0.9	0.4	0.6	0.8	0.9	0.9	0.7	0.7	0.7	0.5
Pneumonia	1.5	0.8	0.8	0.6	1.1	0.2	1.0	1.1	1.1	0.9	1.1	1.1	0.7	0.5
Whooping Cough	1.7	—	1.6	1.2	1.1	1.0	0.8	0.6	0.9	0.9	0.5	0.5	0.5	0.2
Miscellaneous and Unknown	2.1	20.4	26.7	19.8	18.6	23.7	14.7	25.9	15.4	14.2	15.1	18.6	20.7	18.5

II. CAUSES OF DEAFNESS IN MICHIGAN SCHOOL FROM 1883 TO 1912

	1883 1884	1885 1886	1887 1888	1889 1890	1891 1892	1893 1894	1895 1896	1897 1898	1899 1900	1901 1902	1903 1904	1905 1906	1907 1908	1909 1910	1911 1912
Total Number	302	336	342	350	343	365	428	412	441	447	451	404	361	354	353
Congenital	7.0	18.8	23.1	26.3	24.2	26.3	25.2	30.3	28.8	31.5	32.8	36.6	35.7	35.0	31.2
Meningitis	28.8	28.1	23.1	23.1	21.3	15.8	15.6	14.5	10.2	9.2	4.6	8.6	9.5	8.8	8.2
Scarlet Fever	12.2	11.8	12.3	11.2	9.0	9.6	9.5	9.7	9.5	9.3	7.6	6.9	5.8	3.6	4.5
Brain Fever	6.2	6.5	4.8	3.7	5.2	6.9	6.6	6.3	5.4	3.8	3.8	2.7	2.5	2.3	1.0
Typhoid Fever	4.6	3.6	4.1	4.3	4.7	1.9	1.8	1.4	2.5	2.2	1.3	1.0	1.4	1.5	1.7
Measles	3.6	4.1	3.9	2.9	2.6	1.4	0.8	1.9	3.2	3.1	2.9	2.9	4.1	3.4	3.1
Diphtheria	0.6	—	—	0.3	0.3	0.3	0.2	0.2	0.4	0.2	0.4	0.5	0.2	0.3	0.3
Catarrh	0.6	0.6	0.9	0.8	0.9	1.1	1.9	—	2.9	3.5	3.3	2.8	1.9	2.5	0.8
Various Fevers	2.9	1.5	2.0	2.6	3.0	4.4	4.4	1.7	2.9	2.9	3.3	2.5	0.5	2.0	1.4
Whooping Cough	1.3	1.2	1.5	1.5	1.5	3.0	3.8	3.6	2.7	2.5	3.1	3.4	4.4	4.8	5.1
Pneumonia	—	—	—	—	—	—	—	—	0.2	0.2	0.4	—	0.7	0.6	0.8
La grippe	—	—	—	—	—	—	—	—	0.9	1.1	1.6	1.5	3.0	2.3	—
Miscellaneous and Unknown	32.2	23.8	24.3	23.3	27.3	29.3	30.2	30.4	30.4	31.5	34.9	30.6	30.3	32.9	41.9

III. CAUSES OF DEAFNESS IN PENNSYLVANIA INSTITUTION FROM 1843 TO 1912