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both being to thicken the mixture; and in some cases the
practice has been to at once freeze the mixture; in others, in
order to economise the consumption of ice, the heated liquid
has been allowed to cool naturally, under conditions to which
reference will again be made.
(iv) This method of manufacture was only met with in one case.
A freezing mixture is bought which contains all the materials
in a dry powder, and all that is necessary is to boil a certain
quantity of this in milk, and subsequently freeze it. This "ice
cream" was found to be wholesome.
The important stage of the operation would appear to be that between the
boiling and freezing.
Professor Klein, in his report, called special attention to the fact that the
majority of the specific pathogenic bacilli discovered in several of the
samples were of a non-sporing variety, and that, therefore, if originally
present in the material, would have been destroyed by boiling, and,
if found subsequently, must have gained access to the material while
cooling.
The subsequent freezing, while it might inhibit such bacillus, would
certainly not destroy it, and on ingestion and melting its growth
and development would again commence.
Now the effect of boiling such a mixture would be to sterilize it to a
considerable extent, and destroy all the benign or protective
organisms usually present. If, therefore, the material were stored
while cooling in dirty and insanitary places, where infective organisms
could gain access thereto, such organism, free from all interference
of saprophytic bacilli, would be under the most favourable conditions
for their rapid multiplication. In other words, the mere fact of the
previous sterilization would greatly increase the possibility of danger,
provided that the pathogenic organism found an entrance.
If this be true, then such ice creams as were stored under improper
conditions, and especially those which were exposed thereto for any
length of time, would be found especially dangerous.
As a matter of fact this was usually found to be the case.
MILK AND DIARRHŒA.
Infantile Mortality.—Buchan and Mitchell demonstrated that, taking a
period extending over thirty years in London, the death curve of both sexes
at all ages, and from all causes showed (I) a winter upward curve from a
minimum in the middle of October rising to a maximum in December and
January, falling more slowly again to a minimum reached in the middle of
June; and (2) a summer upward curve commencing in the middle of June,
reaching its maximum at the end of July and beginning of August, and
falling more slowly to a minimum in the middle of October. This summer
Jpyramidal curve is practically confined to the third quarter of the year, the
months of July, August and September.