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I put forward this suggestion in a tentative way as possibly explaining certain of
the cases in which the appearance of pus has been presented. In other cases it may
well be that the suggestion of inflammation is a true one, for amongst the immense
herds of cows furnishing the factory milk there must be some unrecognised cases of
mastitis.
Cultural Results from Sediments of Machine Skimmed Milks.
I here tabulate the results of cultures from 42 tins:—
1. Staphylococci, pure, or in overwhelming predominance - 30 tins.
2. Staphylococci and Bacillus colt in roughly equal abundance - 5 „
3. Mixture of various Bacilli, &c., Staphylococci relatively few- 7 „
It will be seen from these figures that pure cultures of staphylococci are by no
means always found, and, indeed, the large proportion of samples in which I
obtained them is probably due to the fact that 28 out of the 42 tins thus
examined were from a certain factory, the product of which was under suspicion. All
but one of these 28 tins yielded almost pure growths of staphylococci. That this need
not be so is seen by the seven tins in the third group, which yielded a relatively scanty
crop of various bacteria, with only occasional colonies of staphylococci, and to which no
bacteriologist could raise any objection.
A difficult question remains for consideration, namely, the wholesomeness of a
condensed milk containing an abundance of staphylococcus pyogenes aureus and albus.
I am not able to offer a decisive opinion on this point. On the one hand it is
certain that these microbes are the cause of inflammatory suppurative affections in man,
when they gain access to the tissues, and the resistance of the patient is sufficiently
low. On the other hand, we bear these organisms on our skins and mucous membranes,
where they live as saprophytes without impairing health so long as our resistance is
normal. I cannot adduce evidence that the swallowing of such a dose of staphylococci as
would be contained in the amount of a condensed milk consumed in a single meal
would produce any prejudicial effect. But it must be remembered that we are here
dealing with a product which may be kept for months before it is used, and if, as I
think possible, the staphylococci multiply in the tins, the content of the milk in
staphylococcal endotoxin, from dissolution of many of the cocci, may become considerable.
I dare not therefore affirm that such milks are harmless. In the six instances in which
I injected the sediment from condensed milks, all of which contained abundant
staphylococci, into guineapigs, no acute suppuration was produced, though in four cases
a local inflammatory swelling occurred, subsiding after a few days. The guineapig is
not as a rule susceptible to infection with staphylococci unless these are of high
virulence, so that too much stress must not be laid on this negative result.
My own opinion is that the presence of staphylococcus pyogenes aureus in large
numbers in a condensed milk is objectionable. I cannot prove that it is dangerous,
though I suspect it. The presence of living and perhaps multiplying pathogenic
organisms in a preserved food cannot be regarded with indifference, even though such
organisms are normally present on the skin and mucous membrane.