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12
THE ZYMOTIC DISEASES.
Having said so much by way of general introduction, I now propose,
before entering into details on the subject of population,
births, deaths, etc., to consider specially the sickness and mortality
from the principal diseases of the Zymotic class, and subjects
naturally arising out of this topic.
The "Class" of diseases called Zymotic, comprises four "Orders."
The first order, "Miasmatic," includes, among others, the diseases
which the Registrar-G-eneral calls" the seven principal diseases of
the zymotic class," still classing under the generic term "fever"
the three distinct fevers, "Typhus," "Enteric," and "Simple
continued." These diseases have a high interest for sanitarians,
being of a more or less preventable character: it is the custom,
moreover, to regard the death-rate from them, and the proportion of
deaths from them as compared with deaths from all causes, as an
index of the sanitary condition of a district. But, without underrating
the importance of this relation it needs be said that there are
limitations to the applicability of the test which must be borne in
mind if we would draw sound conclusions. What I mean can be
best explained by an illustration or two founded on our own local
observations within the last few years. Thus Measles was very
fatal in 1878 ; the deaths were far above the average: it was, so
to speak, the zymotic disease of the year. In 1879, on the other
hand, the deaths from Measles were below the average; but the
reduced mortality—evidence of the diminished prevalence of the
disease, was almost the corollary of the excessive prevalence and
fatality of the malady in the previous year. In saying this, I do not,
of course, ignore the fact that one epidemic of a zymotic disease may
be more severe than another; still less am I forgetful of the fact that
the fatality of an epidemic is largely influenced by the means taken, rathe
neglect to take means, to limit the spread of infection. Diarrhoea
may be cited as an illustration of quite another kind. The mortality
from this disease among infants was excessive in 1877; the
mortality in 1878 was far below the average; but the diminished
mortality in the second year had no relation to the excessive mortality
in the first: the conditions were altogether different. The
summer season of 1878 was cold and wet: in a cold and wet summer
the mortality from infantile diarrhoea is always low, just as it
is always high when the summer is hot and dry, as it was in 1877.