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27
It is a well-known fact in laboratories that pathological
germs may, under certain conditions, become attenuated of
intensified in their effects. It is also held that the virus of
Scarlet Fever may become attenuated or intensified. It is a
rare occurrence to notice successive cases, infected one from
the other, to exhibit symptoms of the same degree of intensity.
The source of infection in a fatal case may have been an
individual suffering from the mildest of symptoms. The
intensity of the symptoms, of course, depends upon two
factors—the seed and the soil. Children with enlarged tonsils
and adenoids, for instance, usually exhibit symptoms of a
severe type.
But apart from the susceptibility of certain individuals,
the virus sometimes loses "if not its infective potencv, at any
rate its power of reproducing typical scarlet fever on normal
soil. The virus, in fact becomes attenuated or recessive."
On the other hand a process of intensification often occurs,
and this latter phenomenon was exhibited during the recent
outbreak.
The outbreak commenced in the autumn of 1907, andi
continued throughout 1908, and up to the beginning of the
fourth quarter of 1909.
Throughout the earlier part of the epidemic the majority
of the cases exhibited very mild symptoms, but during the last
quarter of 1909 the symptoms were of a severe type, and this
latter fact rendered the control of the disease easier.
Elementary schools rank first in importance as centres,
where infectious diseases are spread amongst school children.
It is generally assumed that there are two methods by which
the infection is spread in schools—the direct and the indirect
method.
The indirect method (such as dust, slated, &c.) by which
the infection is spread will be dealt with later. Its importance
has probably been magnified by interested persons, who thereby