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9
per cubic centimetre. Similar results have been obtained elsewhere,
and in London some milk from "good class shops" examined last
May contained nearly five million bacteria. It is obvious from these
figures, which the mind fails to grasp, that mere numbers cannot be of
very much practical importance; but they are evidence of pollution
which may or may not be harmful. Milk, as secreted in a healthy
cow, is a perfectly sterile fluid, and with sufficient precautions it can
be obtained from the animal and kept in a sterile condition. But in
actual life it never is. The enormous number of organisms commonly
present is due to the many channels by which they gain access, and to
their rapid multiplication in the fluid. They enter at the time of
milking, during treatment and preparation. during transit, and after
delivery. Many, indeed, are the pitfalls by the way, and the state of
the milk described is not surprising when the circumstances are considered.
In the first place, disease of the udder, and notably tuberculosis,
may be the source of pathogenic bacteria in the milk ; then
the orifice of the ducts is open to the air and the fluid remaining in
them after milking constitutes a first.rate hotbed for micro.organisms,
so that the "fore milk," or that first drawn, always contains some and
often an enormous number. If these dangers are escaped. the dust
and dirt from the animal's coat, from the air of the byre, and from the
hands of the milker are all prolific sources of contamination. Then
there are the vessels in which it is drawn and which, as I have
always pointed out, are, under the prevailing system of milk delivery,
viz.: the leaving of cans on the doorstep, peculiarly susceptible to
dust contamination in hot, dry weather. In preparation, again,
similar dangers arise from the air of the dairy and the utensils used.
Transit is very important. The milk travels in churns, which are
probably never clean and are often very dirty, and the great distances
covered allow ample time for the growth and multiplication of
organisms. The average distance from which the seven great railways
bring milk to London is two hundred miles, and some of it
travels over four hundred miles. It reaches the customer, at the
earliest, twelve or fourteen hours after milking, which is sometimes
extended to twenty.four or thirty.six hours. Finally, the chances of
pollution in the shop and after delivery from added water, dust, and
dirty jugs are, perhaps, the greatest of all. A recent estimate, based
on the study of six hundred and thirty outbreaks, attributes 17 per
cent. of the typhoid epidemics to polluted milk. The infective
material is most commonly derived from polluted water, which may
be used to wash out the vessels or to dilute the milk. Numerous
cases are on record in which this connection has been proved. Other
probable channels of infection are dust conveyed by the clothes and
hands of persons in attendance on some one suffering from the
disease, or possibly by flies. Too much care cannot be expended by
all, especially where there are infants, in attaining a spotless cleanliness
wherever milk is concerned,