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the disease even when living, as is often the case, in close association
with advanced cases of tuberculosis. To some of the children,
delicate, thin and hirsute the name 'pre-tubercular' was applied,
and it has been held that these are cases of primary infection. The
appellation was unfortunate and has acted as a cloak for many
sins chiefly of omission, in the shape of insufficient investigation
of cases of this kind. Very few of them show evidence of tuberculosis
in later life, and the condition of some of them would probably
be found on closer examination to be due to non-tuberculous
causes such as bad housing, malnutrition, intestinal parasites,
rheumatism or even specific disease.
The question of pulmonary tuberculous infection in childhood
is of great importance and the solution of this problem of immunity
may well lead to a clearer insight into the disease as a whole.
A further point which is shown in Table I. is that the point of
maximum mortality for both sexes occurs at the age of 25, i.e.,
the 'young adult' type of disease is the most fatal. The figures
for new cases show that this type of disease is also the most
prevalent. In the case of females the mortality curve and the
maximum peak conform closely to those for the County of London
as a whole. In the case of males, however, the young adult type
appears to be more prominent than in London. Since the middle
of the nineteenth century there has been a steady drop in the
tuberculosis mortality throughout the country. The decline as
Brownlee showed is most naturally to be regarded as the
ebb of a long epidemic wave to be succeeded perhaps, indeed
probably, by the rise of the next wave in its turn—unless science
can find the way of interference—and its explanation can only
be given by further study. In London, a great change has
occurred since the war. If the mortality curves for 1911 and
1926 be compared (Diagram I.) it will be seen that the peak of
maximum female mortality has entirely changed from the 'middle
age to the young adult type, whereas in the male curve there
is now a small though definite peak at the ages of 20 to 25 which
in 1911 was hardly noticeable. In England and Wales there has
of recent years been an increase in mortality in early adult life,
coinciding with a decline at middle age, and it is quite possible
that we are now on the threshold of a new epidemic wave (of
the early adult type).