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31
As possible clues to the etiology of the disease we have the facts
that chimney-sweepers suffer out of proportion to the rest of the
population (although, in Germany they do not appear to contract
Cancer especially frequently, vide report of the German Committee
for Collective Investigation of Cancer, analysed and tabulated by
Professor C. Hirschberg) while workers with coal enjoy some slight
degree of exemption. Local irritation or injury is a strongly predisposing,
if not exciting factor, especially among those with congenital
vulnerability to the disease ; and when we add that in certain
districts Cancer is more rife than in others we have almost exhausted
the stock of our present knowledge. This varying prevalence over
different areas is found in Germany to be largely accounted for by
variations in the average duration of life in the different districts, but
in England and Wales, Dr. Tatham has shown in the supplement to
his 55th annual report, that if the Cancer rates are corrected for
differences in age and sex distribution even then the variations in
the rate from 1881-1890 were as great as from 2,250 per million for
London to 1,574 for Monmouthshire.
We have therefore everything to learn and practically an open
field for investigation. Is the excellent working hypothesis of the
infection theory correct? Are the related incidences which appear
to point to the contagiousness of Cancer (of auto-infection (lip to lip,
etc.), and the reported cases of Cancer-a-deux) coincidences merely,
or are they due to the slight infectiousness of a generally prevalent
micro-organism ? Is the virus formed inside the body or does it gain
access from without? What about Cancer houses and Cancer
districts? Is our present information sufficient to warrant the
conclusions that the disease is most rife in low-lying districts with
surface deposits of alluvium and sub-soils of clay, and districts which
are liable to flooding? With reference to the existence of Cancer
houses the entire evidence in support depends on death certificates
and such evidence may very easily lead to erroneous deductions. If
there are Cancer houses, what is it that determines a Cancer house ?
Is it resistant and persistent infection, or is it something proper to
the house or site and quite independent of infection from a preceding