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In the above table it will be noticed that the Welsh and Irish form
a very large group. The Welsh males are usually ex-miners who have
come to London to find work. Cases of Silicosis in association with
tuberculosis have been found in this group. The female patients work
as Domestic Servants or Shop Assistants, whilst there are large
numbers of Irishmen employed as Labourers. The Indian patients
are nearly all Students.
It should be noted that the figures given in the above Table do
not refer to all dispensary patients but to notified patients only.
Variation in natural resistance to Tuberculosis.
The majority of adults have been infected with tuberculosis at
some time or other. In relatively few cases is this infection followed
by active disease. In those persons in whom it occurs it is probable
that the infecting dose of tubercle bacilli has been large and repeated,
and there have also been present one or more of those factors which
lower the body resistance. In young adult life—especially in females
during the onset of puberty and adolescence—there appears to be a
marked lowering of this resistance to tuberculous infection. In
addition, it must be remembered that natural resistance varies within
very wide limits in individuals, and in different nationalities. Those
whose forebears have lived in towns for centuries, are, generally, (like
the Jewish people) less susceptible than the peoples who have remained
isolated until comparatively recent times. The North American Indians
who died of tuberculosis in large numbers form a striking example of
this; the white man introduced a new disease to which they had little
resistance through previous infection. If, in addition, there are famine,
malnutrition and privation it is clear that the resistance of a susceptible
people will be lowered even more. Differences in susceptibility are
well demonstrated in the British Isles. The inhabitants of the West of
Scotland and Ireland, and the rural districts of Wales are much more
prone to attack than, say, the Londoner or the Wessex farmer. The
people of North Wales, for example, have lived for centuries in the
Welsh uplands in comparative isolation and they were not brought
into contact with tuberculosis until fairly recent times. Wessex
was the seat of, perhaps, the earliest civilisation in Britain and
the people there were in contact with outside influences more than a
thousand years ago. These two groups of people when they develop