hey were capable of living within the human organism.
It has thus happened that each observer has indicated as the cause of
malaria a different variety of alga, whichever he found to be most
abundant in the swampy ground that he had to examine. Thus Salisbury has
indicated the _palmella gemiasma,_ which is found with us in places
perfectly free from malaria, while it is often wanting in malarious
marshes in the center of Italy; Balestra, a species of alga which is as
yet indeterminate; Bargellini, the _palmogloea micrococca;_ Safford and
Bartlett, the _hydrogastrum granulatum;_ and Archer, the _chitonoblastus
oeruginosus_. There is not a single one of these species the parasitic
nature of which has been demonstrated; and as regards the two last named
varieties, it can be positively denied that they are capable of producing
a general infection, for the diameter of their spores and filaments is
greater than that of the capillary blood vessels.

It was only in 1879 that Klebs and myself, after having been thoroughly
freed, by a long series of preparatory studies, from the unfortunate
paludal idea, undertook together some investigations in malarious
districts of the most varied character, marshy and not marshy. We employed
the system of fractional cultivation, making experiments on animals with
the final products thus obtained. We felt ourselves justified in
recognizing the malarial ferment in the _schizomycete bacillus_. The
numerous researches made subsequently by us, and by many other observers,
in the soil and in the air of several malarious localities, as well as in
the blood and in the organs of men and animals specifically infected, have
put it henceforth almost beyond doubt that we really have to do with a
schizomycete. Very recently, MM. Marchiafava and Celli have succeeded in
demonstrating that the germs of this schizomycete attack directly the red
blood-globules, and destroy them, causing them to undergo a series of very
characteristic changes which admit of easy verification, and which render
certain the existence of a malarial infection.

Several observations made recently in Rome tend to demonstrate that the
schizomycete of malaria does not always assume the complete bacillary form
described by Klebs and myself; but this morphological question possesses
no further interest for the hygienist. For him the essential thing is to
know that he has to deal with a living ferment which can flourish in soils
of very var