View report page

110
Syphilitic disease of the tongue or female external generative organs and tuberculosis of the skin
(lupus) are liable to end in Cancer. Workers in tar, aniline or paraffin, chimney sweeps and mule
spinners are apt to suffer from Cancer in special parts as a consequence of repeated irritation by the
particular agent concerned.
Two recently expressed views of the nature of Cancer require, perhaps, special mention.
(i.) Gye and Barnard's Theory.—These workers, as the result of experiments with certain special
varieties of malignant growths in animals, have come to the conclusion that there are two factors
invariably concerned in the production of Cancer, viz., (a) a filter passing virus widely distributed
in animals and man and not peculiar to any species, and (b) a chemical substance peculiar to each
species and to each variety of cancerous growth, the nature of the malignant growth being determined
entirely by the nature of this substance. In their view neither the non-specific virus nor the specific
chemical substance is capable by itself of causing the formation of a malignant growth, which depends
on the concurrent action of these two factors. Barnard, moreover, claims to have demonstrated the
Cancer virus microscopically with the aid of light of very short wave-length.
There are at present certain grave difficulties in the way of accepting the results of these workers,
and much independent work will be necessary before their theory can be finally accepted or rejected.
(ii.) Blair Bell's Conception.—Another recently formulated conception of Cancer is that of
Professor Blair Bell and his co-workers at Liverpool. These investigators consider that research can
be more profitably directed to the investigation of the true nature of the cancerous process than to
the search for a specific cause. They regard malignant growth as a " reversion to the nourishmentproviding
proclivities normally possessed in a special degree by the chorionic epithelium " (i.e., those
cells which serve to attach the developing embryo to the wall of the womb). In accordance with this
conception the " predisposing causes " or " exciting factors " of malignant development are those
agencies which produce an " unhealthy " condition of the cells, i.e., permanent injury to the cells
without their death, the formation of a new growth which is innocent or malignant being determined
by the condition of the cells on -which the common factors are acting. Much interesting chemical
and biological work has been done by this group which they believe affords valuable confirmation
of their views, and it was by deduction from the above premises that they were led to the discovery
of a new treatment for Cancer which has met with some success in specially selected cases. Nevertheless
experience has repeatedly shewn that such success cannot be regarded in itself as a proof on the
correctness of their views, which can only be regarded by the scientific world, as indeed they are
regarded by these workers themselves, as constituting a working hypothesis.
4. Cancer Mortality.—In considering this aspect of the subject the important questions
from a Public Health point of view are the following :—
(i.) Is the death rate from Cancer really increasing, and if so, is this increase confined to
any particular country or part of the world ?
(ii.) At what ages does the increase occur ?
(iii.) What parts of the body are most concerned in this increase.
(1) The death rate per 1,000 of the population for England and Wales has gradually increased
from 0.32for 1851-60 to l.12for 1911-20, 1.21 for 1921 and 1.29 for 1924. Even when full allowance
has been made for the increased proportion of the population that is now in those ages at which Cancer
commonly occurs it is still clear that the recorded mortality has trebled in the space of two generations.
" During the period of 20 years from 1901 to 1921, in which Cancer increased by 20 per cent., the
general death rate fell by 32 per cent., that of infants by 45 per cent., and that from Tuberculosis by
38 per cent., while substantial declines were recorded in respect of most other causes of mortality."
(Memo, of Departmental Commission on Cancer.) The question as to whether this increase is a real
one has been long and hotly debated. It has been argued that improvements in diagnosis and more
accurate certification were sufficient to account for the apparent increase; but it is now generally
admitted that these factors, though undoubtedly contributory, cannot account for the whole of the
recorded increase. Taking as an instance Cancer of the tongue, in males we find an increase from
38 per million living in 1901 to 53 in 1921. Again, in the case of Cancer of the female breast, the
figures shew an increase from 148 per million living in 1901 to 190 in 1921. This increase in Cancer
mortality is not by any means confined to our own country, but is seen, wherever statistics are available,
to apply to all countries and races.
(2) As regards the age periods at which this increase occurs the latest available returns
shew that the death rate from Cancer is not increasing for males up to 45 years of age or for females
up to 60. The most rapid increase is in extreme old age.
(3) Lastly, the Registrar General's returns bring out the fact that the increase of deaths attributed
to Cancer is referable to certain anatomical regions and not to others. Thus for males the
main increase falls on the alimentary tract, especially the stomach. The liver and gall bladder and
the skin shew no, or only a slight, increase. For females the increase, although it falls mainly on the
alimentary tract (stomach and intestines) affects also the breast, while the womb, ovary, liver and gall
bladder, rectum and skin shew little or no increase. Moreover the incidence is very unequally distributed
among the different situations, the whole curve of incidence being often quite different for
different organs. A progressive increase up to the highest age periods is characteristic of the face,
lip, mouth, bladder, urethra and breast only. The other organs shew a distinct diminution in the
highest age periods.