not this paludal notion, for experience taught
them long ago that malaria is produced nearly everywhere--in marshy
districts as well as in those which might almost be called arid; in a
volcanic soil as well as in the deposits of the Miocene and Pliocene
periods and the ancient and modern alluvia; in a soil rich in organic
matters as well as in one containing almost none; in the plains as well as
on the hills or mountains. The word malaria (bad air), which it is the sad
privilege of Italy to have lent to all languages to express the cause of
intermittent and pernicious fevers, represents, then, among the majority
of our rural populations, the idea of an agent which may infect any sort
of country, whatever may be its hydraulic and topographical conditions,
and whatever may be its geological formation. This word, therefore, is the
one best suited to designate this specific ferment in question, and I have
on this account, employed it and its adjectival derivatives in order not
to resuscitate the idea of the exclusively paludal origin of the morbific
agent.

I shall not tarry long to speak of the nature of this ferment, for the
studies bearing upon that point, although far advanced, are not yet
completed. I may remark, however, that the idea that the ferment is formed
of living organisms is a very old one, and has not arisen suddenly because
of the modern theories of the parasitic nature of disease. From the time
of Varrar (who believed that malaria was made up of invisible mites
suspended in the atmosphere) to our own day this theory has been several
times advanced by hygienists. Independently of the general considerations
which led Rasori, and later Henle, to formulate the doctrine of the
_contagium vivum_ of infection (long before the progress of microscopical
science had revealed the existence of living ferments), there were
peculiar circumstances as regards malaria which should have impelled minds
to look in that direction, even in times long past.

Some of these circumstances are of a nature to strike every serious
observer, and deserve a few moments' attention. How could one maintain,
for example, that this ferment is a product of chemical reactions taking
place in the ground, when it is seen to remain constantly the same
whatever may be the composition of the soil from which it emanates! As
long as the paludal theory held sway, the chemical interpretation of this
identity of the product in every latitude was easy. R