That the relative incidence is more than a temporary accident is shown by the approximate recurrence of the frequencies after ten years.
In proportion as latitude and occupation influence the occurrence of cancer, race is diminished as a cause. It is reduced still further by other considerations. The rate for Austria in 1906-10 was 78, for Hungary 44. Here the race is the same: the difference must be social. Austria averaged higher in wealth, education, medical development. This fact would tend to have a double effect. First, among the more backward population, a certain proportion would die of internal cancers difficult to diagnose, without the cause being recognized, owing to insufficient medical treatment. Second, the general death rate would be higher. More children and young people would die of infectious or preventable disease, leaving fewer survivors to die of cancer in middle and old age. Wherever, on the other hand, a public is medically educated, and typhoid, smallpox, diphtheria, tuberculosis claim fewer victims, the proportion of those dying of cancer, nephritis, heart diseases, increases. Such an increase is noted everywhere, and goes hand in hand with a longer average life. The alarm sometimes felt at the modern “increase” of cancer is therefore unfounded, because it is perhaps mainly apparent. If a larger percentage of the population each year died of old age, it would be a sign that sanitation and medicine were increasingly effective: evidence that more people lived to become old, not that age debility was spreading.
Consequently, a high degree of modern civilization must tend to raise the cancer rate; and any group of people will seem relatively immune from cancer in proportion as they remain removed from attaining to this civilization. In Hungary, from 1901-04, the cancer deaths were 239 among the owners of large farms, 41 among the owners of small farms; 108 among employing blacksmiths, 25 among their employees; 114 among employing tailors, 32 among employed tailors. Obviously these pairs of groups differ chiefly in their economic and cultural status.
Here too lies the explanation of why the South African negro shows a rate of only 14, the United States negro of 56; also why the Chinese rate is as low as 5 in Hongkong, rises to 19 in Manila, and 26 in Hawaii, while the closely allied Japanese average 62 for the whole of Japan—as compared with 50 for Spain, which is pure Caucasian, but one of the most backward countries in Europe. In Tokyo and Kyoto the rate soars to 73 and 90 respectively, just as in the United States it is about 10 higher for the urban than for the rural population.
Within the United States, also, the rate rises and falls almost parallel for whites and Negroes according to locality; as,
| 1906-10 | White | Negro |
|---|---|---|
| Memphis | 59 | 34 |
| Charleston | 73 | 37 |
| Nashville | 74 | 55 |
| New Orleans | 86 | 73 |
If allowance is made for the facts that the negro population of the United States is poorer and less educated than the white; that it lives mainly in lower latitudes; and that it tends to be rural rather than urban, the comparative cancer death rates for the country of negro 56 and white 77 would appear to be accounted for, without bringing race into consideration.
In short, what at first glance, or to a partisan pleader, would seem to be a notable race difference in cancer liability, turns out so overwhelmingly due to environmental and social causes as to leave it doubtful whether racial heredity enters as a factor at all. This is not an assertion that race has nothing whatever to do with the disease; it is an assertion that in the present state of knowledge an inherent or permanent connection between race and cancer incidence has not been demonstrated. If there is such a connection, it is evidently a slight one, heavily overlaid by non-racial influences; and it may be wholly lacking.
The case would be still less certain for most other diseases, in which environmental factors are more directly and obviously influential. Racial medical science is not impossible; in fact it should have an important future as a study; but its foundations are not yet laid.