Scientific American Supplement, No. 458, October 11, 1884 by Various

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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 they 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 varied composition, and without the presence of which neither
marshes nor stagnant pools of water are capable of producing malaria.

We must not think, however, that all earth containing this ferment is
capable of poisoning the superjacent atmosphere. Popular experience,
certain modern scientific investigation, and the facts which one can often
verify when the soil, which was malarious in ancient times and which has
since ceased to be so, is turned up to a great depth, all agree in proving
that the ground remains inoffensive as long as it is not placed in certain
conditions indispensable for the multiplication of this specific ferment.
Up to this point the organism lives, so to speak, in an inert state, and
may remain so during centuries without losing any of its deleterious
power. There is nothing in this fact that ought to surprise us, since we
know that the life and the power of evolution belonging to the seeds of
plants of a much higher order than these vegetable organisms constituting
ferments, may remain latent for centuries, and may then revive at once
when these grains are placed in the conditions suitable for their
germination.

Among the conditions favorable to the multiplication of the malarial
ferment contained in the soil, and to its dispersion through the
superjacent atmosphere, there are three which are absolutely essential,
and the concurrence of which is indispensable for the production of bad
air (malaria). First, a temperature which does not fall below 20 deg.C.
(67.5 deg.F.); next, a very moderate degree of permanent humidity of the soil;
and finally, the direct action of the oxygen of the air upon the strata of
earth which contain the ferment. If a single one of these three conditions
be wanting, the development of malaria becomes impossible. This is a point
of prime importance in the natural history of malaria, and it gives us the
key to most of the methods of sanitary improvement attempted by man.

Let us see first what can be done in this direction without the labor of
man. For nature herself makes localities salubrious by _suspending_ for a
greater or less time the production of malaria. It is thus that winter
brings about in every country a freedom from malaria which is _purely
thermic_, for it is due simply and entirely to a sinking of the
temperature below the required minimum. Indeed, if the temperature in
winter rises above this minimum, there are often sudden outbreaks of
malaria. Sometimes, during very warm and dry summers, the heat extracts
all the humidity from the malarious soil, and thus procures for us a
freedom from the disease which is _purely hydraulic_. This may continue
for a long time (as happened in the Roman Campagna during the years 1881
and 1882), but may also be completely destroyed by a single shower. Nature
also sometimes renders a district healthy in a manner _purely
atmospheric_, by covering a malarious soil with earth which does not
contain the malarial ferment, or with a matting formed of earth and the
roots of grasses growing closely together in a natural meadow.

In the attempts of purification by suspending the malarial action, which
have been devised by man, the same thing has been done; that is to say, it
has been sought, to eliminate at least one of the three conditions
essential to the development of the specific ferment contained in the
infected soil. Naturally, they have not thought of bringing about a
thermic purification, such as nature produces in winter, because of the
impossibility of moderating the action of the sun; but they have tried
from all time to procure hydraulic or atmospheric purifications, and
sometimes to combine these together in a very happy way.

The hydraulic systems are very numerous, for the problem which is
presented, namely, that of depriving the ground of its humidity during the
hot season, necessitates different solutions according to the nature and
the bearing of the soil. Sometimes this is done by digging open or closing
ditches intended to draw away large bodies of water. At other limes a
system of drainage is established, by means of which the water is drawn
out of the earth and its level is depressed, so that the upper malarious
strata, exposed to the direct action of the air, are deprived of moisture
during the hot season. This system of drainage is not a modern invention;
the Italian monks understood it as well as, and even better than, we do.
In deep and loose soils they used sometimes, just as we do now, porous
clay pipes; but when the subsoil was formed of compact and nearly
impermeable matters, they employed a system of drainage, the extent and
grandeur of which astonishes us. It is that of drainage by cavities,
applied by the Etruscans, Latins, and Volsci to all the Roman hills formed
of volcanic tufa, the tradition of which I have found still preserved in
some countries of the Abruzzi.

We may sometimes establish a double drainage, from below and from above;
that is to say, to drain the subsoil, and at the same time increase the
evaporation of water from the surface of the ground. It is well known that
clearing off the forests of malarious countries has often proved an
excellent means of making lands salubrious which were before too damp;
for, by removing every obstacle to the direct action of the sun's rays
upon the ground, we cause an increase of evaporation from its surface, and
may thus be enabled to exhaust the superficial strata completely of their
water during the hot season. In very moist lands, which lend themselves
readily to deep drainage, the combination of the latter with a clearing
of the surface has, in almost every quarter of the globe, rendered
possible a very widespread and sometimes a quite lasting freedom from
malaria. But, although a nearly universal experience proclaims this fact,
there is a school which, following in the footsteps of Lancisi, maintains
the contrary opinion, that it is necessary to preserve the forests in
malarious districts, and even to increase their extent, since the trees
filter the infected atmosphere and arrest the malaria in their foliage.
This strange theory was formulated by Lancisi in 1714, on the occasion of
the proposed clearing of a forest belonging to the Caetani family, and
lying between the Pontine Marshes and the district of Cistema. Lancisi was
completely imbued with the paludal notion, and consequently believed that
the very severe malaria of Cistema was brought by the winds from the coast
marshes, instead of being produced in the soil surrounding the district,
which was then covered by this forest. He believed then that the forest
acted as a protective rampart, and he prevented its being cut down. But
toward the middle of the present century the Caetani had the woods cleared
off from the entire belt of land surrounding Cistema. Twenty years later I
was able to show that Cistema had gained greatly in salubrity. I published
my observation in 1879, and, naturally, was taken to task rather sharply
in the name of the sacred tradition. Happily these recriminations led our
Minister of Agriculture to have the question studied by a special
commission. This commission, after a conscientious examination extending
over three years of all the malarious localities in the province of Rome,
has just published its report,[1] the conclusions of which are entirely in
accord with the facts of universal experience. They were not able to
verify a single fact in support of Lancisi's theory, while they found many
of the same nature as that of Cistema, and which have resulted in
overturning the theory entirely.

[Footnote 1: Della influenza dei boshi sulla malaria dominante nella
regiona marittima della provincia di Roma. Annali di Agricoltura, No. 77,
1884. Roma: Eredi Botta.]

It has also been thought possible to practice drainage from above by means
of plantations of certain trees which would draw considerable moisture
from the earth, a method which might really be serviceable in some
malarious districts. But in accordance with the idea that malaria is a
product of paludal decomposition, the trees selected have almost always
been the _eucalyptus_. It has been maintained that trees of so rapid a
growth ought to drain the soil very actively, and also that the aroma of
their foliage ought to destroy the miasmatic emanations. I have hitherto
been unable to verify a single instance of the destruction of malaria by
eucalyptus plantations, but I do not consider myself justified in denying
the facts which have been stated by others. There is nothing to oppose the
admission that these plantations, when properly made, may sometimes have
been of great utility. I maintain frankly, however, that they have not
always been so, and that it is necessary to guard against the
exaggerations into which some have allowed themselves to fall in recent
times. Such exaggerations might have been avoided if, instead of talking
about these plantations on the basis of a theoretical assumption, the
results only had been studied in places where the eucalyptus abounds. It
would then have been known that even in the southern hemisphere, the
original home of the eucalyptus, there are eucalyptus forests which are
very malarious. This fact has been demonstrated by Mr. Liversige,
professor in the University of Sydney, Australia. Among us also, although
everybody was convinced by the statements of the press that the locality
of the Tre Fontaine, near Rome, had been freed from malaria by means of
the eucalyptus, people were disagreeably surprised by an outbreak of very
grave fever occurring throughout the whole of this colony in 1882, a year
in which all the rest of the Roman Campagna enjoyed an exceptional
salubrity. If, alongside of these hygienic uncertainties, we place the
agricultural uncertainties, we must conclude that it is necessary to
contend strongly against this fanatical prejudice in favor of the
eucalyptus tree. These plants are, in fact, very capricious in their
growth. In full vegetation during the winter in our climate, they are
often killed instantly by a sharp winter frost, by damp cold, by the
frosts of spring, or by other causes which the botanists have not yet been
able to determine. At other times, if the winters are very mild, these
plants grow too rapidly in height, and then are broken short off by
moderately strong winds. It should further be mentioned that these
plantations are sometimes very expensive. In fact, if the earth contains
too much water, it must be drained under penalty of seeing the roots of
the eucalyptus rot. Then again, if the subsoil is compact, it is necessary
to dig deep trenches in order to give room to the long roots of these
trees, and often indeed these trenches must also be drained, as is done
for olive trees. The conclusion evidently is that it is better to confine
ourselves to hydraulic methods of promoting the health fulness of a
locality, the immediate effects of which are less uncertain. And then,
when the local conditions are such as to make it desirable to try the
effects of plants possessed of strongly absorbing powers, it is better to
choose them from among the flora of our own hemisphere. This is more sure,
and will cost less.

Simple hydraulic methods of purification, even the most perfect, do not,
however, produce permanent hygienic effects, since the moisture necessary
for the multiplication of the malaria in the soil is so slight that these
effects may be compromised by anything whatever that is capable of
restoring a moderate degree of humidity to the ground during the hot
season. It has often been thought that a suspension of malarial production
would be better assured by suppressing at the same time the humidity of
the soil and the direct action of the oxygen of the air upon the
superficial strata of earth which contain the ferment. This has been
successfully accomplished by the system of overlaying (_comblees_). This
consists in covering the infected soil by thick layers of uninfected
earth, carried there either by the muddy waters of rivers or by the hand
of man. At the same time the steady drainage of the surface and
underground water is provided for. Last year I advised our Minister of War
to undertake in another form a hydraulico-atmospheric purification of the
district of the Janiculum surrounding the Salviati Palace on the Via della
Longara, by draining the soil carefully and covering with a layer of very
close turf all the parts of the surface which could not be macadamized. It
would seem as if this system had been rather successful, since there has
not been this year a single case of fever in the _personnel_ of the new
military college, established in the Salviati Palace; while in the Corsimi
Palace, which is situated on the same side of the Via della Longara, but
which looks out upon that part of the Janiculum which is still uncovered,
there have been some fatal cases of fever.

Furthermore, we have had in Rome, during the past few years, some very
evident proofs of the efficacy of atmospheric methods of purification. I
will confine myself to the relation here only of the most striking
instance, one which has been furnished us in the building up of new
quarters of the city. There was much discussion at first as to whether the
improvements should be undertaken in the parts where they now are or in
the valley of the Tiber, for the uncovered lands of the Esquiline and of
the Quirinal were malarious, and, as nearly everybody then thought that
the malaria of Rome was carried into the city from the coast marshes, it
was supposed that this state of things was irremediable. We opposed to
this view the fact of the salubrity of the Viminal, which is situated
between the Esquiline and the Quirinal, and which ought to be as unhealthy
as the two other hills were the malaria of the latter imported into the
city instead of being indigenous. Believing it to be indigenous, we hoped
that by shielding the surface of these hills from the direct action of the
air (by building houses and paving the streets), the malaria would cease
to be produced there. That is precisely what has happened, for the new
quarters are very healthy. But the malaria is only held in abeyance, and
is not definitely overcome; for if an extensive excavation is made in
these hills, and the contact of the air with the malarious soil is thus
re-established, during a hot and damp season, the production of malaria
commences anew. A complete atmospheric purification is nevertheless the
most stable of all the methods of obtaining a suspension of malarial
production, but unfortunately its realization is very limited, for it is
restricted to inhabited localities and to sodded surfaces.

The ideal method of insuring freedom from malaria should be to obtain a
permanent immunity, that is, to be able to modify the composition of the
infected soil in such a way as to make it sterile as regards malaria,
without taking from it the power of furnishing products useful for the
social economy. But all the elements indispensable for obtaining such a
result fail us utterly just here. We do not yet know what ought to be, in
general terms, the composition of a soil incapable of producing malaria,
yet retaining those properties which are suitable for vegetation. When we
shall have arrived at this first stage, there will still be a long road to
travel; and the most difficult part will be to discover a practical means
of imparting this salutary composition to all the numerous varieties of
malarious soils.

Scientifically, then, in the present state of our knowledge we are unable
to affirm anything on this point. Practically, we are not much further
advanced. It is very probable that the combination of hydraulic
purification with a forced cultivation of the soil has sometimes
determined changes in its composition by which it has been rendered
sterile as regards malaria. If that has happened, it has happened by
chance, and we are unable to reproduce the result at will; for we have not
all the data which might enable us to understand how it has come about.
Most of the purifications obtained in ancient times, by means of forced
cultivation, continued during centuries, have not been definite at all,
but the production of malaria has been simply suspended. Hardly was the
regular cultivation of the fields interrupted than the production of
malaria recommenced. Among the numerous examples that I might cite in this
connection, I will limit myself to that of the Roman Campagna. This seemed
to have been made permanently healthy under the Antonii, but after the
fall of the empire it began again to produce malaria, as if the forced
cultivation through so many centuries had never been.

One might, strictly speaking, be content with such a result, and boldly
undertake forced cultivation of all malarious districts, without stopping
to ascertain whether the freedom from malaria so obtained would be
definite, or whether the production of the poison were only suspended.
Unfortunately, one is never sure of arriving at such a result, and no one
can say, _a priori_, whether the forced cultivation of a given malarious
tract will render it healthful. It must always be remembered that the
first effect of forced cultivation, which requires 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 such a nature that a
single attack may suffice to ruin the constitution for life. Collective or
_racial acclimation_ certainly existed in the past, at a time when
specific remedies for pernicious malaria were unknown; and even later,
when the employment of these remedies was very limited. The acclimation
was due to a natural selection made by the malaria upon successive
generations, from which it took away, almost without opposition, all those
who possessed but a feeble individual power of resistance to the specific
poison, while it spared those who possessed this power of resistance in an
extraordinary degree. The first were, according to the Grecian myth, _the
human victims destined to appease the monster or demon who opposed the
violation of the territory over which he had up to that time exercised an
absolute sovereignty_. The second became the founders of the race, and
through them, from generation to generation, the collective power of
resistance to the malaria was progressively increased. In our own days a
like selection may take place among barbarous races, as it does among the
cattle and the horses in a malarious region, but it has become an
impossibility among civilized nations. By means of the specific remedies
which we possess, the use of which is now so general, the lives of a large
number of individuals whose resisting powers are very feeble are
preserved; and these individuals beget others whose power of resistance to
the action of the specific poison is still more feeble. This results after
a number of generations in the physical degradation of that part of the
human race which inhabits malarious countries.

We cannot, therefore, in the future, count upon the assistance of external
natural forces to increase the power of resistance of human society
against the assaults of malaria. Such an object can be obtained only by
artificial means. It has been sought to attain this end by the daily
administration of the salts of quinine, of the salicylates, and of the
tincture of eucalyptus, each and every one tried in turn. But the salts of
quinine are dear, exercise a prompt, though very transient anti-malarial
action, and, when administered for a long time, disturb rather seriously
the functions of the digestive and nervous systems. The salicylates, when
well prepared, are rather dear, and there is as yet no proof that they
possess prophylactic powers against malaria. The alcoholic tincture of
eucalyptus is useful in malarious regions (as are all the alcoholics,
beginning with wine) in quickening the circulation of the blood; may it,
perhaps, also act as a preservative against light attacks of malaria?
Possibly. But it is very certain that it possesses no efficacy in places
where malaria is severe. It will suffice to prove this to recall the two
epidemics of fever which afflicted the colony of the Tre Fontaine, near
Rome, in 1880 and 1882. Everybody was attacked, and there were several
cases of pernicious fever, although a good preparation of eucalyptus is
manufactured in the place and is distributed largely to the colonists
during the dangerous season of the year.

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