cinoma. Among the male Arabs nine tenths of all cases of carcinoma occur in the face, which is especially exposed to the rays of the sun, and in the women carcinoma is more frequent in the vagina than in the uterus. Carcinoma of the gastro-intestinal tract is relatively rare. Also among the inhabitants of East India and Ceylon and among the Chinese we find a lower cancer rate than in Europe. In Japan however cancer seems to be relatively frequent as far as the available statistics indicate.
Also among the Indians in the reservation of the "United States cancer is considerably rarer than among the white population (J. Levin). Differences in climate can therefore not be held responsible for these great differences in the cancer incidence. But is it due to inheritable race characteristics or differences in mode of living, preceding infection with other diseases? This question we can not answer definitely at the present time. Some facts however are of interest in this connection. W. Renne found that among the natives of Sierra Leone cancer is very rare; but since a more intimate intercourse between the natives and immigrated whites has taken place, cancer has increased in Sierra Leone. But even in this case we are unable to decide whether this increase is due to changes in the conditions in life or to the intermarriage between whites and natives. In the United States we also find that within the last fifty years there has been a considerable increase in the cancer incidence among the colored population. Cancer of the uterus, which was formerly rare among colored women, is now more frequent among the colored population than among the white. Here again we can not be sure how much of this increase is due to changes in the mode of living, to increase in the inflammatory conditions of the uterus, and how much to intermarriage.
In the case of the relative rarity of uterine cancer among Norwegian women, we again do not know whether it is due to the relative infrequency of preceding infections of the uterus or whether it is a question of race. Interesting problems thus present themselves as to the relative importance of race and of external conditions in the origin of cancer. More definite knowledge could be gained if in statistics a distinction were made between negroes and mulattoes; it would also be of interest to establish the frequency of uterine cancer in the first and second generation of Norwegian women in this country, especially distinguishing between those interspersed among the rest of the population and those living in close rural communities in which the original customs are preserved.
We mentioned already that on the whole carcinoma occurs especially in old age. In the United States the average of death from carcinoma is 60 years for males and 58 years for females. Between 45 and 64 years 7 per cent, of all deaths in the male and 16 per cent, of all
