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exposure to the exciting cause; indeed there were strong reasons
for believing that this co-called "incubation period" did not exceed
48 hours. Under these circumstances, and after the other possible
causes had been excluded, the sudden outcrop of many cases in
a localised area pointed to a milk epidemic.
It may be of further interest to briefly state the main reasons
that made me hesitate before I pronounced the milk to be the
cause of the infection:—
I.—The outset of the outbreak was not characteristic of
milk infection. Instead of there being 5 infected houses on
November 9th, and 8 more on November 10th, one would have
expected nearer 10 times this amount, seeing that the supply was
a large one.
II.—The theory of milk infection did not explain away the
very marked and special fall of the outbreak upon Hendon Lane,
since we should expect to find the infection carried all along the
track of supply of the particular cart and cans that conveyed the
milk to Hendon Lane. What really happened was that, at the
commencement of the outbreak, of 22 houses supplied in
Hendon Lane 5 were infected, whereas of 56 houses supplied in
other streets only 6 were infected.
III.—Children were not mainly affected. Among the cases
of which I was informed there nearly twice as many people over
20 as there were children under 10.
IV.—It is general knowledge that cows may suffer from
certain eruptions on teats and udders without conveying any
infection to the milk—whereas it is equally established that milk
in such cases can convey the infection of Scarlet Fever, if not of
Diphtheria—the throat being primarily affected in either case.
V.—I had been able to satisfy myself that in Hampstead,
St. Pancras, and Stoke Newington there were at the time many
somewhat similar throat cases.
The conclusions which I came to were:—That the outbreak
was favoured by the excessive rainfall and variable
temperature of the preceding fortnight, upon a cold, damp soil,