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in tuberculosis causation must explain the changing relationships of the death.
rates in the two sexes with advancing age. They must assume a difference by
inheritance, or by selection, in favour of males at the younger ages and in favour
of females at the older ages. There is no evidence for such differential hereditary
endowment among brothers and sisters. I should say, however, that they have
at no time, to my knowledge, addressed themselves to this problem or attempted
to explain the phenomenon.
" Racial Variability in the Tuberculosis Death-Rate.—The third outstanding
fact in a description of tuberculosis is the marked difference in the rate of mortality
which prevails in the various nativity groups composing the population of the
country. In a previous study we found that the death rate was lowest among
those born in Russia, who, in these two states are for the most part Jews. This
interesting fact has been observed again and again not only in the United States,
but in other parts of the world where the mortality of Jews has been carefully
studied in comparison with that of their neighbours. Tuberculosis does not appear
to be as fatal among them as among other races. The disease when it appears is
more often of long duration. The rates are also very low among the Italians.
"... It is difficult for anyone confronted with these facts to escape the
conclusion that an inherited racial immunity is a factor in the development of
tuberculosis . . .
"On the other hand, there are certain allied facts to be considered which throw
additional light on this interesting phenomenon. The rates among the Jews and
the Italians are not everywhere uniformly low, but show considerable variation
from place to place, reflecting, in fact, the better and worse conditions among which
the Jews and Italians of this country live . . .
"Variations in Economic Levels.—Another important fact in our discussion is
the difference in the tuberculosis death-rate in the various economic strata of the
population . . . How shall this set of facts be explained ? The environmentalists
rest their case on the hardships of the life of the poor as we have already intimated ;
the constitutionalists on the superior endowments and vigour of the selected or
'fit' groups who make up the well-to-do and richer classes of the community as
distinguished from the poor. . . .
"Occupation in Relation to Tuberculosis.—The incidence of tuberculosis in
various occupations also throws light on the nature of the disease, on how it may
be caused, and how it may be controlled . . .
"... The theory of the geneticists would demand that those who are engaged
in various occupations are selected somehow in accordance with their various grades
of resistance and inherited ability to withstand tuberculosis. Some occupations
undoubtedly attract weaker individuals. On the other hand, the effect of the
industrial environment on the life of the worker is very clear-cut, even if often
masked by the influences of economic condition, grade of intelligence, and other
elements which affect life. The enormously high tuberculosis death-rate of tin miners
and of stone cutters is very clearly the result of the injury done to the lung tissue
by the material with which they work . . .
" Recent changes in the Tuberculosis Death-Rates.—Finally, we shall consider the
changes in the tuberculosis death-rate in recent years. As we have seen, the tuberculosis
death-rate in the general population of the United States has fallen 50 per cent,
in a twenty-year period .... The decline, moreover, has not been uniform
in all the groups of the population, but has favoured males more than females, white
lives more than coloured lives, and certain definite age periods more particularly
than others . . . Certainly as applied to the United States, there is no evidence
that the changes that have occurred in the last decades have come about through
any improvement in the racial constitution of the people. The eugenists have not
lost an opportunity to say that in their opinion no improvement has occurred, and
if anything, there has been deterioration. They have pointed to the decline in the