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THE CAUSES OF DISEASE. 283
whole city of New York, but its victims were among
those who were weakened by other causes, and were
living in all unhealthy conditions. Of the 5,000 who
died of cholera in New York in 1849, 3,000 were
buried in the Roman Catholic cemetery. They were
mostly poor Irish and Germans, living crowded to
gether, in the most unhealthy parts of the city, and
surrounded causes by many of disease. The other two
thousand were exhausted by intemperance, by sensual
ity, or iu some way unable to resist the diseasing in
fluence. There was no danger to any really healthy
person.
And this is true of all external causes of dis
ease. Iu proportion to the energy of our vitality and
the purity of our lives, is our power to resist and over
come the causes of disease.
There is another preventive to particular forms of
disease, in that power of the system to adapt itself to
unusual and even unnatural conditions, which may be
called the power of habit or acclimation. Persons get
accustomed to the malaria of yellow fever, for instance.
" Custom is every thing," we hear it said. It is much,
not every thing. Habit enables a man to take twenty
grains of opAum at a dose; when he began, five grains
would have killed him. Custom enables a man to
smoke or chew tobacco all day long ; when he began, a
single quid or half a cigar made him deadly sick. Cus
tom enables a man to bear with a smoky house, a scold-
ino- wife, or any other annoyance. It is in this way
that men bear so much evil, live in filth, eat flesh,
breathe foul air, use tobacco and whisky, and become
hardened to all the miseries of life. are They accli
mated. But the whisky, and malaria, and pork, and