ted
that malaria is caused by a living organism whose successive generations
accumulate in the soil, the interpretation of this fact becomes very
simple.

There are, finally, _peculiarities in the local charging of the atmosphere
with malaria_ which can be explained only in this manner. If the malarial
miasm were composed of gaseous bodies emanating from the soil, or rather
of chemical ferments formed beneath the ground and raised into the air by
gases or watery vapor, the charging of the atmosphere with the specific
poison ought to arrive at its maximum during the hottest part of the day,
when the ground is heated the most by the sun's rays, and when the
evaporation of water and all chemical actions attain their maximum
intensity. But this is very different from what actually occurs. The local
charging of the atmosphere is always less strong during the meridian hours
than at the beginning and the end of the day, that is to say, after the
rising, and especially after the setting, of the sun. Now it is precisely
at these hours that the difference between the temperature of the lower
layers of the atmosphere and that of the surface of the ground is the
greatest, and that the ascending currents of air starting from the ground
are the strongest. If malaria consists of solid particles contained in the
soil, one may readily understand how their elevation _en masse_ into the
atmosphere should take place especially at these two periods of the day.

All these facts, which can be easily verified if the subject of malaria be
studied on the spot and without any preconceived notions, explain the
tendency which has always been manifested to attribute this specific
poisoning of the air to a living organism which is multiplied in the soil;
and they also explain the ardor with which hygienists have applied
themselves to the production of the scientific proof.

Unfortunately the investigations undertaken for this end have for a long
time been fruitless, for the preconceived paludal theory has led
investigators to occupy themselves exclusively with the inferior organisms
inhabiting marshes. Among these organisms they studied especially the
_hyphomycetes,_ which had already acquired so great an importance in
dermatology; and their entire attention was concentrated upon the aquatic
algae, without even taking the precaution to determine whether the
varieties which they thought to be malarial were found in all malarious
swamps, or whether t