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THE CAUSES OF DISEASE. 281
ship with yellow fever at our quarantine has given the
disease to persons residing at the leeward.
Typhus is perennial in many parts of London, in low,
filthy places, and around crowded graveyards.
But whatever the nature of these causes, there
seems to be some specific agency which determines the
nature of the disease. With the same kind of persons,
suffering from the same causes, we have at one time
dysentery; at another, erysipelas; at another, hospital
gangrene; at another, typhus, or ship, or jail fever; at
another, yellow fever ; at another, cholera. We have
also special animal poisons determining to measles,
scarlatina, small pox, etc.
We have also the malaria, or telluric,
or aromal
causes of intermittent fever, or fever and ague. This
disease is attributed to decaying vegetation, but it is
found in dry deserts, and is wanting in the most fertile
localities. Stagnant water is said to cause it, but we
find it on dry prairies, and miss it amid swamps and
morasses. Localities which seem to the observer pre
cisely similar, and even but a few miles are apart, en
tirely different in this respect. I believe that the
presence of stagnant water aids in bringing
out the
poison. So does any disturbance of the soil, as digging
a canal, or a grading railroad. The cause seems to me
to be in the soil, and not in decaying matter, either
animal or vegetable. It is not found on certain geolog
ical strata, nor above a certain degree of latitude. As
we go South it is more intense, and is combined with
other malaria, to produce
laria of the Carolina rice swamp,
remittent fevers. The ma
or of the African
coast, is almost certain death to a white man from a