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some of which are known to bo harmful to man. The same street dust
is blown into milk shops, whore milk is usually kept for sale in open
vessels. Milk forms an excellent brooding ground for bacteria, and it is
therefore easy to see why town infants who are fod mainly on milk
should suffer from diarrhoea, that is to say, if wo accopt the origin of
diarrhoea as a dust disease. Road dust is practically free from horsedung
in country districts, where summer diarrhœa is hardly known. The
influence of hot summers most likely lies in furnishing the amount of
warmth requisite to the growth and multiplication of the microbes. Rain
washes the microbes from the air and from exposed surfaces, hence the
smaller amount of diarrhœa in wet summers. According to my theory,
epidemic diarrhoea is duo to a surface pollution derived from street dust.
Tho practical lessons to be gathered from the application of the
theory are plain and simple. First of all the necessity of unremitting
activity in the scavenging of streets and of houses is emphasized,
especially does this apply to courts and alleys and passages which should,
in my opinion, be systematically flushed with hose, at any rate during
the third quarter of the year, when the disease is rampant. In this way
the purifying influences of an abundant rainfall may be obtained by
artificial means. It is necessary, however, that the road and other paving
should be washable—that is to say, it must be hard, smooth, and
impermeable. The best roadways are those of hard asphalte or concrete,
while all passages, courts, yards, alleys, and byways, should be smoothly
and evenly paved with bricks, flags, or one of the hard, smooth paving
surfaces. The need of daily scavenging of house refuse need only to be
mentioned.
Perhaps one of the most important of all points is that relating to
milk. Milk should be sterilized and kept in closed vessels ; if exposed to
the air of towns, either in shops or in the larder, it cannot fail to become,
sooner or latter, infected with unwholesome germs. There can be no
doubt whatever that the infection of summer diarrhoea is conveyed in the
vast majority of cases, to town children, through the agency of milk. This
fact explains why the disease is so much less common among children
fed at the breast than among those brought up on the bottle.
The question arises, how is this milk to be purified of the poison of
summer diarrhoea ? The answer lies in the sterilization of milk. The
milk should be sterilized at the farm and kept in sterilized bottles until
opened for use. So far as one can see under the modern complex
conditions of milk collection and milk storage there is no other path of