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35
Cases have been reported in which the disease is supposed
to have taken two to four weeks to devolop, but most
authorities refuse to accept these long incubation periods as
authentic.
We may take it that the incubation period does not exceed
seven days, and that it is very seldom longer than four. It
is stated that in milk epidemics the incubation period is
shortened,' but usually the vast majority of patients take from
two to three days to develop their symptoms.
I think it may be fairly assumed that all the primary
cases could have been infected on the same day, but in that
case the date must have been either April 19th or April 20th.
On the other hand, if the infection had been a continuous or
an intermittent, and not a transient one, the contamination may
have occurred on any dates between April 13th and April 26th.
Apart from the dates on which these cases had occurred,
an incident had occurred at the dairy which would have made
it highly improbable for the milk to have been the means of
spreading infection after April 21st.
On April 20th, the child of the foreman at the dairy was
notified as suffering from Scarlet Fever. Every possible precaution
was taken at the house and at the dairy to prevent
the contamination of the milk. The child was immediately
removed to the hospital, the premises were disinfected and the
father was not allowed to resume work until April 24th. In
addition, all the milk was pasteurized on and after April 21st.
When the dairy was visited on April 24th the milk was still
being pasteurized.
There was no evidence by which the infection of the milk
could be traced to the child of the foreman. It may be stated,
though, that the Scarlet Fever patient, even [in the beginning