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visitations of these diseases, has not yet given us the
least insight into their causal relations, or even into
the laws which govern their manifestations. Looking
back, for example, at the several epidemic visitations of
these diseases during the last twenty years, we notice
that alvine disorders (cholera) were extremely severe in
1855 and 1866; that continued fever was unusually
fatal from 1855 to 1857, in 1859, and from 1862
to 1866; that scarlet fever has pursued a regular
periodic course of two years of severity and two of
intermission, beginning with 1855 and 1856, and
ending with 1871 and 1872; that measles was
epidemic in 1858 and 1859, in 1861 and 1862, in
1864, in 1866, and 1868; and that whooping cough,
croup, and diphtheria were more than commonly
active in 1855, in 1858 and 1859, in 1861 and
1862, in 1865 and 1866, in 1869 and in 1872;
while the years which were most free from total
epidemic influence were 1858, 1860, 1865, 1867, and
from 1870 to the present time. But none of these
periods, whether epidemic or otherwise, presented
any such marked peculiarity of season, or other
natural phenomena, as would enable us to interpret
the actual causation of such diseases, or the so-called
epidemic constitution of the period.
With respect to the distribution of disease in the
various districts of the City during the year, I have
to direct your attention to the sixth table of the
Appendix, as well as to the following, which