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50
Annual Report of the London County Council, 1910.

An account of puerperal fever in the practice of mid wives will be found on page 94.
Seasonal prevalence of and mortality from, infectious diseases.
Diagram (V) shows composite curves based on the number of cases of the several infectious
diseases notified and deaths therefrom registered in the weeks of the period 1891-1910. The
curves relating to deaths are reproduced from the Annual Summary of the Registrar-General
for the year 1910. The curves indicating cases may be compared with those relating to the years
1890-1903, included in the annual report for the year 1903. No conspicuous or large differences are
found by this comparison. The curves of 1891-1910 relating to deaths may be compared with curves
relating to deaths in 1841-1900, included in the annual report for the year 1900, and with curves
based on the deaths of 1841-1910 shown in the Annual Summary of the Registrar-General for 1910«
The curves of smallpox for the several periods exhibit no conspicuous differences. The curve
of measles shows in the later period a conspicuous increase in the spring months, and decrease in the
autumn months. The curves of whooping-cough manifest no striking differences, except that there
is a slight tendency of the whooping-cough curve in the later period to change in the same direction
as the later measles curve. No conspicuous changes are observable in the curves of enteric fever,
erysipelas and puerperal fever. The resemblance between the mortality curves of erysipelas and
puerperal fever is deserving of note.
The scarlet fever mortality curve of the more recent period shows conspicuous flattening. The
autumnal high prevalence is in this period much diminished, and the spring low prevalence is less
marked. These changes coincide with a declining death-rate. A conspicuous feature in the more
recent mortality curve is a marked depression occurring a little later than the depression in the notified
case curve which has been discussed in these reports in connection with the school holiday in August.
The diphtheria mortality curve of the later period presents no conspicuous differences from the curve
of the earlier period, except that it also exhibits, but in more marked degree, the same depression
as in scarlet fever, occurring a little later than the depression in the notified case curve which has also
been discussed in relation to the school holiday in August. This depression is indicated, but to a
less extent, in the curves relating to the earlier periods.
The question whether this August decrease in the number of scarlet fever and diphtheria
cases notified was in any important degree due to exodus from London at the time of the summer
holiday was discussed as long ago as the year 1894 (6), but no reason was found for assuming that this
exodus was to any substantial extent responsible for the decrease. It was pointed out that the
decrease in the cases notified among children of school age began about a week later than that of the
closure of the schools, and that a smaller decrease occurred among children of a pre-school age and of
persons of a post-school age a week still later, suggesting that the diminished prevalence among the
two last sections of the population was due to diminished infection from the children of school age.
Increase in the number of cases notified was found about a week after the re-opening of the schools. It
might be anticipated that if exodus from London were a dominant factor in determining the diminished
(a) See footnote (by page 41. (b) Prasidential address to the Epidemiological Society. Trans. 1894.