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Diarrheal affections, including cholera and dysentery, occasioned 293 deaths; a
number which exceeded the mortality from similar affections, even of the cholera
year 1860, when diarrhoea, cholera, and dysentery together occasioned 245 deaths.
The number of cases recorded in the public practice of the parish was 2514. In
1867 it was 1750, which, with the exception of 1866, was the largest number
registered up to that time. The summer outbreak of these affections commenced
as usual in the fourth week of June, but previously to this the number of cases had
been more numerous than is customary. The maximum number of cases was
attained in the first week of August, after which they declined. The severity with
which in any year the diarrhoeal season sets in, in the month of June, depends very
clearly upon the heat and dryness of the atmosphere, and similar conditions govern
the prevalence of diarrhoeal affections throughout the summer quarter. This being
so, the meteorological conditions of last year sufficiently account for the high
number of cases recorded in the month of June and the succeeding months of July
and August. An analysis which I have made of the records of sickness here, as
compared with the weather during the past twelve years, shows that nothing like
an abrupt increase of diarrhoea happens until the mean temperature rises
above 60°. Last year the outbreak of diarrhoea followed this observation, for
in the second week of June the mean temperature rose from 60.3° to 65 4°, and
in the same week the first indication of the commencement of the diarrhoeal wave
was given. I have also found that the summit of the diarrhoeal wave is not reached
until about two weeks after the highest summer temperature has been attained. So
also last year, the highest mean temperature of any week, 70'7° was attained in the
third week of July, and the largest number of cases of diarrhcea was recorded two
weeks later, viz.: in the first week of August, the greatest atmospheric dryness having
been observed in the preceding week.
Measles, as I pointed out in my last Annual Report, is a disease which only
spreads extensively among us every second year, having thus a biennial period of
cyclical recurrence as a severe epidemic. As a rule, however, it spreads, more or
less, every spring and autumn, never being completely absent; thus it was due, as
a severe epidemic, last year. The number of deaths registered from this disease was
147. In 1867, they only amounted to 39. The number of cases occurring in the
public practice of the parish was 838; in 1867 it was 336. The experience
of the past twelve years teaches us that, although the autumnal epidemic,
commencing usually about the month of November, is the more constant and
certain in its occurrence, and also the more fatal in consequence of its pulmonary
complications, yet that on the whole the spring epidemic, usually commencing in
May, is that which is the wider in its extension among our population. Comparing
the prevalence of measles with conditions of season and weather, I have arrived,
among others, at the following inferences, from observations made during the
years 1857 to 1868:—1st. That the condition promotive of an outbreak of measles,
in any year, is a mean temperature between 43° and 48°, especially if assisted by