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14
of London districts for the year he discusses. It will be seen that the effect of the holiday is well
marked in each group in that year.

On page 24 of his report he writes—
"Is it not probable that the decreased number of notifications during the school holiday is in a
"great measure due to the fact that many children are then taken into the country, leaving fewer
"susceptible people in London? This explanation would account for the persistence of the notifications
"in the poorer districts concurrently with their decrease in other parts of London."
I have already discussed this question in 1894,* and expressed the opinion that this hypothesis
did not suffice to explain the August decrease. It may, of course, be a small factor, but certainly
the assumption that the migration of children from London was explanative of the decrease,
would necessitate further assumptions that children 0-3 years of age go out of town for their
holiday later than the older children, and that, inasmuch as the extent of the August decrease
varies greatly in different years, that the number of people leaving London for an August holiday
must vary in like degree. On the face of it this is improbable; the explanation of this difference
is probably to be found in the extent to which diphtheria is in one, as compared with another
year, spreading in the schools. With regard to the fact that the August holiday effected in
1895 less reduction in diphtheria in the eastern and southern districts as compared with the western,
this may likely enough be due to the greater tendency of children in poorer districts to maintain
relationship with their schoolfellows in the streets during holidays.
On pages 24 and 25 he discusses the experience of other towns, and publishes a table showing
the number of notifications in seven English towns in each of the weeks from the 22nd to the 40th in
each year of 1891-95. The towns referred to are Manchester, Salford, Oldham. Liverpool, Sheffield,
Newcastle-on-Tyne and Birmingham, and he writes "these figures taken as a whole show scarcely any
perceptible fluctuations of the incidence of disease which could fairly be attributed to school influence."
The number of cases of diphtheria notified in these towns is, however, very small, and require more
detailed examination before any sure opinion can be expressed on the subject. I have in the
following table shown the results obtained by grouping the cases in respect to age and also in
three equal periods—(1) before holiday influence; (2) period of holiday influence; and (3) period
subsequent to holiday influence. As far as was practicable I have shown these results in the towns
mentioned above, and have added those of certain other towns for which I was able to obtain the
necessary figures. The table certainly shows marked decrease in the number of notifications in the
period of holiday influence.
* Presidential address to the Epidemiological Society, November, 1894.