AGE.—Carcinoma is exceedingly rare under 20 years of age, most malignant tumors at that period being sarcomata. After 25 the number of deaths from cancer about doubles each five years up to 40, and then increases steadily, until the actually greatest number of deaths, 6,909 (3,071 males, 3,838 females), occurred between 60 and 64 years of age, after which they decreased steadily; there were 267 deaths at 90 and over, 8 of them being 100 years and over. At no period did the deaths of males exceed that of females, and from 35 to 39 years of age the latter were almost three times that of males.
OCCUPATION.—Many attempts have been made to trace the influence of occupation upon the incidence of cancer, but thus far very little of practical interest has been demonstrated; the difficulties concerning this investigation are immense, owing to absence of essential and accurate data. There have been many lists presented, but few of which agree as to details, and all need to be corrected as to the proportion of those living at different ages. There is also the question as to the effect of local or general agencies; thus, as to the result of local injuries on the skin, and also in regard to other agencies, whatever they may be, which produce internal cancer; for tables of occupation do not generally refer to sex, age, or location of the disease.
First, to dismiss the question as to the direct result of local injuries in inducing cancer of the skin, which, at the most, caused only 3.7 per cent of all cancer deaths in 1914, we may cite a few instances in which this appears to be pretty well established.
The occurrence of epithelioma as a direct result of repeated and protracted exposure to X-ray is familiar to all, and is particularly interesting because it occurs commonly among younger persons, and at a time of life when epithelioma is rare; and especially also because the X-ray is constantly effective in curing epithelioma. The rarity of epithelioma resulting from X-ray, considering the enormous amount of exposure which must have occurred in making and using X-ray tubes, implies, however, that there must be some other cause also at work. It has been urged, therefore, that the skin tissue being altered and weakened from repeated and protracted exposure to X-rays, more readily falls prey to some of the chemical or other irritating agencies which have been observed to be followed by epithelioma.