res an overturning of the
soil by means of the plow, the spade, and the pick, is an unfortunate one,
from a hygienic point of view, whenever we have to deal with a malarious
country. Experience has shown, especially in Italy and America, that this
overturning of the soil almost invariably increases the local production
of malaria. And this can be readily understood, since the plowing and the
digging in a soil containing the specific ferment increase the extent of
surface of the ground in immediate contact with the atmosphere. This first
mischievous effect is often gradually weakened by the continued
cultivation, and may end by disappearing. At other times, on the contrary,
it persists obstinately, and one is often forced in desperation to the
resolve to level the ground again and to varnish it, so to speak, with a
thick sowing of grass, if he wishes to suspend or weaken the malarial
production.

However, when the local conditions will permit, it is well to try whether,
by means of forced cultivation of the soil, it may not be possible to
increase the efficacy of the hydraulic method of procuring immunity from
malaria, or of the hydraulico-atmospheric method of "overlaying." The
moment that it is known that this cultivation has frequently been
advantageous, there comes forward a crowd of social reasons which induce
us to attempt it, even though we be persuaded that we are about to engage
in a game of chance. But to dare to attempt it is not all that is
necessary; we need also the possibility of so doing, and just here we find
ourselves in a vicious circle from which it is not easy to emerge. Forced
cultivation cannot be accomplished without the presence of agriculturists
in the region during the entire year; and the agriculturists cannot remain
in the region during the fever season, for they run thereby too great a
risk. For the solution of this question there is but one means: _try to
increase the power of resistance of the human organism to the attacks of
the malaria_. It is to a search after the means of accomplishing this
result that I have devoted myself during the past few years.

There is nothing to hope for, as regards malaria, in acclimation.
_Individual acclimation_ is, and always has been, impossible. The malarial
infection is not one of those a first attack of which confers immunity
from other attacks. It is, on the contrary, a progressive infection, the
duration of which is indeterminate, and which is of suc