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ages. These factors could, of course, all be allowed for by the statisticians,
and the conclusion arrived at that there was a real increase. Another
aspect of the problem was how much of this increase was due to improved
diagnosis. That, of course, could account for an increase in incidence of
disease in the deep-seated organs, but would not be a factor of importance
in superficial cancers which could readily be diagnosed. As an instance,
it could be that in the earlier years deaths of patients might have been
erroneously attributed to pulmonary tuberculosis whereas the true cause
was cancer of the bronchus. The conclusion reached on this point though
was still the disturbing one that there was a real increase in the incidence
of cancer. Since then the over-all picture has improved. There was in
fact, an actual fall to 0·99 in the early 1940's and a further fall to 0·98 by
1946. This decline though has been followed by a gradual rise to 1·00 in
1947, 1·01 in 1950 and 1·02 in 1955. The figures remained the same in
1956, and then fell to 1·01 in 1957. As these figures relate to fatalities,
part of the improvement which has occurred might have been due to
improved means of diagnosis and therefore earlier diagnosis, and also
to an improvement in means of treatment. To what extent these factors
have operated in accounting for a fall in the numbers of deaths for the
earlier years, they would presumably also be acting to hold back a larger
increase than has taken place from occurring.
A breakdown in the figures for the sexes shows that amongst females
the situation is steadily improving. Since the figure of 0·6 in 1947, each
year has seen either a repetition of the figure of the previous year or
something less, with a result that the figure for 1957 was only 0·90.
The position with regard to males is just the reverse. Each year
since 1946 when the figure was 1·03 has seen either a repetition of the
previous year's figure or an increase, with a result that the figure for 1957
had reached 1·18. This deterioration in the position regarding deaths
from cancer amongst males is almost wholly due to an increase in the
number of deaths from cancer of the lung. The only other site showing
an increase is the bladder. The other disturbing increase is in leukaemia.
In spite of all the work that has been done on the subject, the cause
of cancer still remains unknown. It is, of course, known that those
exposed to certain irritants are more likely to have cancer of certain sites ;
but not all those exposed to these irritants develop cancer. Before the
discovery of micro-organisms, much stress was laid on the aetiological
factors which contribute to any disease. In the case of some such as
tuberculosis, it was thought that there was an ingrained pre-disposition
to the disease. The person was said to have a tuberculous diathesis. With
the discovery of the organisms responsible for different infections, less
stress was laid on this aetiological factor. An illness such as diphtheria
for example, was considered to result from the reaction of the host to
the Presence of the particular bacillus. Later it was appreciated that the
Position was not nearly as simple as this. It began to be recognised that
some of the organisms like those capable of causing diphtheria could not
in fact cause the disease. There was a difference in the virulence of the
organism. On the other hand, it came to be recognised that exposure of
Person even to a virulent organism did not necessarily result in illness. If
the person had a resistance, being said to be immune to attack, he did not