consumption in Massachusetts, per 10,000 population:

1851-60 39.9
1861-70 34.9
1871-80 32.7
1881-90 29.2
1891-1900 21.4
1901 17.5
1902 15.9

F. L. Hoffman further points out[60] that in Massachusetts, Rhode Island,
and Connecticut, 1872-1911, the decline in the death-rate from
tuberculosis has been about 50%. "The evidence is absolutely conclusive
that actually as well as relatively, the mortality from tuberculosis in
what is the most intensely industrial area of America has progressively
diminished during the last 40 years."

It will be noted that the great increase in death from consumption in
this area began in the decade following 1840, when the large Irish
immigration began. The Irish are commonly believed to be particularly
susceptible to phthisis. Crowded together in industrial conditions, they
rapidly underwent infection, and their weak racial resistance led to a
high death-rate. The weak lines of heredity were rapidly cut off; in
other words, the intensity of natural selection was great, for a while.
The result was to leave the population of these New England states much
more resistant, on the average, than it was before; and as the Irish
immigration soon slowed down, and no new stocks with great weakness
arrived, tuberculosis naturally tended to "burn itself out." This seems
to be a partial explanation of the decline in the death-rate from
phthisis in New England during the last half century, although it is not
suggested that it represents the complete explanation: improved methods
of treatment and sanitation doubtless played their part. But that they
are the sole cause of the decline is made highly improbable by the low
correlation between phthisis and environmental factors, which was
mentioned above, and by all the other biometric study of tuberculosis,
which has proved that the results ascribed to hygiene, including
sanitorium treatment, are to some degree illusory.

That tuberculosis is particularly fatal to the Negro race is well known.
Even to-day, after several centuries of natural selection in the United
States, the annual death-rate from consumption among Negroes in the
registration area is 431.9 per 100,000 population (census of 1900) as
compared with 170.5 for the whites; in the cities alone it is 471.0.
That overcrowding and climate can not be the sole fac