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Less stress should probably be laid on those staphylococci yielding a white growth.
There is, it is true, a staphylococcus pyogenes albus which is a mere variety of staphylococcus
pyogenes aureus, and seems identical with it in pathogenic powers, but there are also
other comparatively harmless white staphylococci, common on skin surfaces, and
distinguishable from the actively pyogenic form only by more or less elaborate tests.
The Results of Animal Experiment.
I have already alluded to these so far as concerns the absence of any immediate
production of suppuration when sediments from certain of the milks were inoculated
into guineapigs. It is too early to determine whether any of the animals will become
tuberculous ; the object of the inoculations would be frustrated by killing them at this
stage, and the result must be related in a few weeks' time in an addendum to this report.
General Conclusions.
(1) In normal healthy milk, cells are present which are identical with those of
pus. In none of the condensed milks examined did I find these cells in greater number
than might be expected from the natural cellular content of the milk. The suggestion
that such milks contain pus has therefore no warrant.
(2) The bacterial content of a large number of the samples examined seems
unnecessarily high. That it is unnecessary is shown by the fact that in some samples of
machine skimmed condensed milk the number of bacteria is small and their character
unobjectionable. It would appear that the process of Pasteurisation is in the latter case
adequately, and in the former case inadequately carried out.
To set up any numerical standard in this respect might prove difficult if it were
shown that bacteria multiply in condensed milk, because the number would vary with
the age of the sample.
(3) The presence in a condensed milk of staphylococcus pyogenes aureus in any
considerable number appears to me objectionable, but again, for the reason just stated,
it is difficult to suggest any numerical standard. Speaking purely as a pathologist (and
leaving it to those concerned to decide whether the suggestion is practicable), T should
be disposed to condemn a condensed milk the sediment of which yielded a culture of
staphylococci in which staphylococcus pyogenes aureus formed a noticeable element. With
adequate Pasteurisation the absence of this coccus could, I believe, be secured.
F. W. ANDREWES, M.D., F.R.C.P., D.P.H.
St. Bartholomew's Hospital,
December 5th, 1912.