Page:Popular Science Monthly Volume 86.djvu/336

332. Now the interpretation of this result is not simple; in part the higher death rate of the negro is due to economic conditions that are, however, determined largely by racial traits; but, in part, it is probably due to the fact that the negro is not yet adjusted to the white man's civilization. Especially does this folk of jungle origin wither away in our large cities. Similarly, the death rate from tuberculosis is 3 times as great among our Indians as among the whites, and deaths from measles are proportionally greater among Indians than whites. Clearly the grand races differ tremendously in their vitality.

I know there are those who deny that there is such a thing as inherited resistance to disease. But there is at least a family liability to or immunity from various diseases, such as tuberculosis. It is easy to find in our records families in which 10 out of 12 or 14 deaths in a family have been from tuberculosis; as it is easy to find families of which none of the 10 or more members who have died have died of this disease, even when they have died at mature age, and, like practically every person, exposed to the disease. I think, then, we must recognize that non-resistance to tuberculosis is a family trait; and it may be characteristic of a whole locality, provided that locality (like southern California) has attracted many representatives of the non-immune race. We find indeed that, despite its salubrious climate, consumption is a much more common cause of death here than in most other sections of the country; and the high incidence of tuberculosis is found in the children and grandchildren of those who went to California for their health.

Again cancer is a disease whose rate of incidence varies in different parts of the country; it is highest in the state of Maine. Now, I have no doubt that this is due to the presence of one or more races in Maine which are non-immune to cancer. I know that many medical men do not respond favorably to the contention that there is a racial cancer diathesis in man. To be sure, it has been repeatedly demonstrated that such races occur in mice and such human families as we have studied yield the same result as the mice studied and indicate that resistance to cancer is a positive (dominant) trait and that non-resistance appears in the children only when both parents belong to a non-resistant race. And this result is commonest, other things being equal, where cousin marriages are commonest, because that makes it probable that if one parent belongs to a cancer race the other—the cousin—will belong to the same cancer race. Now in rural Maine, cousin marriages are extremely frequent—especially in the islands off the coast, and here we have the conditions for the result—the high incidence of numbers of the cancer race in an inbred community.

Again Huntington's chorea is a fairly common cause of death in certain localities, and it is a racial character as truly as are brown eyes.