We may take these tables together to see how the proportions of deafness from the leading diseases have changed in the course of the several periods indicated, proper allowance being made for the shorter length of time covered in some schools than in others. In respect to scarlet fever, one of the two foremost causes, we find in the New York Institution, the Michigan School and the Maryland School, a distinct and steady decline; in the Pennsylvania Institution a decline of late years, which is especially significant in view of the extended period covered by it; and in the Western Pennsylvania and the Wisconsin School little change, though in the latter there is less than at the beginning. In meningitis, on the other hand, the second of the two most important causes, a marked increase is seen in the Pennsylvania Institution for the entire period, while in the New York a sharp increase is found in the time designated, this being all the more noticeable because of the large proportion already attributed here to convulsions, often a trouble of kindred origin. In the Western Pennsylvania Institution and the Maryland School little change is observed, though in the latter some decline is apparent in the later years. In the Wisconsin and Michigan schools a very strong decline is seen. On somewhat the same order as meningitis is brain fever. It, however, shows little change on the whole, though in the Michigan and Maryland schools and the New York Institution some decline is evident. Of the remaining diseases none plays singly a large part in the causation of deafness, and in most of them the results are similar. Measles, typhoid fever, diphtheria, pneumonia, and whooping cough show, with some fluctuations at times, little change on the whole, beyond certain local differences. In the New York Institution a decline is reported in nearly all. In the Pennsylvania Institution a rather larger proportion for measles is seen in later than in earlier years. In the Michigan School an increase seems to be the case with whooping cough, but a decrease with typhoid fever. In catarrh the results are not so uniform. In the New York and Pennsylvania institutions a decline is manifest, though in the latter a larger proportion is reported than at the beginning. In the Michigan and Wisconsin schools rather an increase is noted. La grippe is only reported occasionally of late years, and its real effects cannot yet be ascertained. With respect to general fevers, their classification is found to be so varying that little can be determined.
We now proceed to make comparison of the proportions of deafness from the principal diseases in a series of years some time past with similar proportions in recent years. The following tables give the several proportions in the American School (Connecticut) in the entire attendance from 1817 to 1844 and from 1817 to 1857, and in the new admissions from 1901 to 1913; in the Ohio School in the entire attendance from 1829 to 1872, and in the average annual attendance in 1904, 1905, 1906, and 1911; in the Iowa School in the entire attendance from 1855 to 1870 and from 1855 to 1912; and in the New York Institution in the entire attendance from 1818 to 1853 and in the average annual attendance from 1899 to 1912.[38]
I. CAUSES OF DEAFNESS IN AMERICAN SCHOOL FROM 1817 TO 1844, FROM 1817 TO 1857, AND FROM 1901 TO 1913.
| PERIOD | TOTAL NUMBER | CONGENITAL | SCARLET FEVER | MENINGITIS | TYPHOID FEVER | MEASLES | WHOOPING COUGH | GENERAL FEVERS | BRAIN FEVER | PNEUMONIA | DIPHTHERIA | CATARRH | UNKNOWN AND MIS. |
| 1817‑1844 | 761 | 44.8 | 5.7 | 6.1 | — | 1.6 | 1.6 | 6.7 | — | — | — | — | 33.5 |
| 1817‑1857 | 1081 | 50.1 | 9.2 | 4.6 | — | 1.8 | 1.3 | 5.3 | — | — | — | — | 27.7 |
| 1901‑1913 | 310 | 35.2 | 7.7 | 11.3 | 3.2 | 1.3 | 1.3 | 1.9 | 5.8 | 0.6 | 1.3 | 1.0 | 29.4 |
II. CAUSES OF DEAFNESS IN OHIO SCHOOL FROM 1829 TO 1872 AND FROM 1904 TO 1911.
| PERIOD | TOTAL NUMBER | CONGENITAL | SCARLET FEVER | MENINGITIS | TYPHOID FEVER | MEASLES | WHOOPING COUGH | GENERAL FEVERS | BRAIN FEVER | PNEUMONIA | DIPHTHERIA | CATARRH | UNKNOWN AND MIS. |
| 1829‑1872 | 1252 | 33.8 | 10.3 | 3.0 | 1.8 | 3.2 | 1.7 | 4.6 | 5.7 | — | 0.3 | — | 35.6 |
| 1904‑1911 | — | 38.9 | 5.0 | 9.2 | 1.4 | 2.8 | 1.7 | 1.1 | 5.3 | 0.5 | 0.5 | 3.5 | 30.1 |
III. CAUSES OF DEAFNESS IN IOWA SCHOOL FROM 1855 TO 1870 AND FROM 1855 TO 1912.
| PERIOD | TOTAL NUMBER | CONGENITAL | SCARLET FEVER | MENINGITIS | TYPHOID FEVER | MEASLES | WHOOPING COUGH | GENERAL FEVERS | BRAIN FEVER | PNEUMONIA | DIPHTHERIA | CATARRH | UNKNOWN AND MIS. |
| 1855‑1870 | 245 | 87.2 | 13.4 | 3.3 | 1.6 | 2.0 | 1.3 | 6.1 | 1.3 | — | — | — | 33.8 |
| 1855‑1912 | 1672 | 26.9 | 10.3 | 14.9 | 1.7 | 2.2 | 1.7 | 0.1 | 7.0 | 0.3 | 0.8 | 1.7 | 32.4 |