An important and influential conference[1] upon cholera was opened in
Berlin at the Imperial Board of Health on the evening of July 26. There
were present Drs. v. Bergmann, Coler, Eulenbrg, B. Fränkel, Gaffky,
Hirsch, Koch, Leyden, S. Neumann, Pistor, Schubert, Skreczka, Struck,
Virchow, and Wollfhügel. The conference had been called at the instance of
the Berlin Medical Society, whose President, Prof. Virchow, explained that
it was thought advisable Dr. Koch should, in the first instance, give a
demonstration of his work before a smaller body than the whole society, so
that the proceedings might be fully reported in the medical press. He
mentioned that Herr Director Lucanus and President Sydow had expressed
their regret at being unable to be present, as well as many others,
including Drs. Von Lauer, Von Frerichs, Mehlhausen, and Kersaudt. Before
the meeting Dr. Koch exhibited microscopical specimens and drawings of the
cholera bacillus, and demonstrated the method of its preparation and
cultivation. The preparations included specimens of choleraic dejections
dried on covering glasses, stained with fuchsin or methyl-blue, and
examined with oil immersion, one-twelfth, and Abbe's condenser; also
sections of intestine preserved in absolute alcohol, and stained with
methyl-blue. There were also cultures in gelatin, etc.
[Footnote 1: A detailed report is published in the _Berliner Klinische
Wochenschrift_ Aug. 4.]
Dr. Koch commenced by remarking that what was required for the prevention
of cholera was a scientific basis. Many and diverse views as to its mode
of diffusion and infection prevailed, but they furnished no safe ground
for prophylaxis. On the one hand, it was held that cholera is a specific
disease originating in India; on the other, that it may arise
spontaneously in any country, and own no specific cause. One view regards
the infection to be conveyed only by the patient and his surroundings; and
the other that it is spread by merchandise, by healthy individuals, and by
atmospheric currents. There is a like discrepancy in the views on the
possibility of its diffusion by drinking water, on the influence of
conditions of soil, on the question whether the dejecta contain the poison
or not, and on the duration of the incubation period. No progress was
possible in combating the disease until these root questions of the
etiology of cholera are decided.
Hitherto the advances in knowledge upon the etiology of other infective
diseases have done little toward the etiology of cholera. These advances
have been made within the last ten years, during which time no
opportunity--at least not in Europe--has occurred to pursue researches;
and in India, where there is abundant material for such research, no one
has undertaken the task. The opportunity given by the outbreak of cholera
in Egypt last year to study the disease before it reached European soil
was taken advantage of by various governments, who sent expeditions for
the purpose. He had the honor to take part in one of these, and in
accepting it he well knew the difficulties of the task before him, for
hardly anything was known about the cholera poison, or where it should be
sought; whether it was to be found only in the intestinal canal, or in the
blood, or elsewhere. Nor was it known whether it was of bacterial nature,
or fungoid, or an animal parasite--e.g., an amoeba. But other difficulties
appeared in an unexpected direction. From the accounts given in text-books
he had imagined that the cholera intestine would show very slight changes,
and would be filled with a clear "rice-water" fluid. He had not fully
recollected the conditions met with in post-mortem examinations had
formerly made, and was therefore at first surprised to meet with quite a
different state of things. For he soon found that in a large majority of
cases remarkably severe lesions were present in the intestines. In other
cases the changes were slighter, and eventually he met with some which, to
a certain extent, corresponded with the type described in text-books. But
it was some time, and after many inspections, before he was enabled to
correctly interpret the varied changes met with. In spite of a most
careful examination of all other organs and of the Mood, nothing was found
to establish the presence of an infective material, and attention was
finally concentrated on the intestinal conditions.
There were cases in which the lower segment of the small intestine, most
marked immediately above the ileocæcal valve, extending thence upward, was
of a dark reddish-brown color, the mucous membrane being covered with
superficial hæmorrhages. In many cases the mucous membrane appeared to be
superficially necrosed, and covered with diphtheritic patches. The
intestinal contents in such cases were not colorless, but consisted of a
sanguinolent, ichorous, putrid fluid. Other cases showed a gradual
transition to a less marked change. The redness was less intense, and was
in patches, while in others the injection was limited to the margins of
the follicular and Peyerian glands, giving an appearance which is quite
peculiar to cholera. In comparatively few cases were the changes so slight
as to consist in a somewhat swollen and opaque condition of the
superficial layers of the mucous membrane, with delicate rosy-red
injection, and some prominence of the solitary follicles and Peyer's
patches. In such cases the intestinal contents were colorless, but
resembling meal-soup rather than rice-water. In only a solitary instance
were the contents watery and mucoid. Microscopical examination of the
intestine and its contents revealed, especially in the cases where the
margins of Peyer's patches were reddened, a considerable invasion of
bacteria, occurring partly within the tubular glands, partly between the
epithelium and basement membrane, and in some parts deeper still. Then he
found cases in which, besides bacteria of one definite and constant form,
there were others also accumulated within and around the tubular glands,
of various size, some short and thick, others very fine; and be soon
concluded that he had to do here with a primary invasion of pathogenic
bacilli, which, as it were, prepared the tissues for the entrance of the
non-pathogenic forms, just as he had observed, in the necrotic,
diphtheritic changes in the intestinal mucosa and in typhoid ulcers.
Passing to speak of the microscopical character of the contents of the
bowel, Dr. Koch said that owing to the sanguinolent and putrescent
character of these in the cases first examined, no conclusion was arrived
at for some time. Thus he found multitudes of bacteria of various kinds,
rendering it impossible to distinguish any special forms, and it was not
until he had examined two acute and uncomplicated cases, before hæmorrhage
had occurred, and where the evacuation had not decomposed, that he found
more abundantly the kind of organism which had been seen so richly in the
intestinal mucosa. He then proceeded to describe the characters of this
bacterium. It is smaller than the tubercle bacillus, being only about half
or at most two-thirds the size of the latter, but much more plump,
thicker, and slightly curved. As a rule, the curve is no more than that of
a comma (,) but sometimes it assumes a semicircular shape, and he has seen
it forming a double curve like an S, these two variations from the normal
being suggestive of the junction of two individual bacilli. In cultures
there always appears a remarkably free development of comma shaped
bacilli. These bacilli often grow out to form long threads, not in the
manner of anthrax bacilli, nor with a simple undulating form, but assuming
the shape of delicate long spirals, a corkscrew shape, reminding one very
forcibly of the spirochaete of relapsing fever. Indeed, it would be
difficult to distinguish the two if placed side by side. On account of
this developmental change, he doubted if the cholera organism should be
ranked with bacilli; it is rather a transitional form between the bacillus
and the spirillum. Possibly it is a true spirillum, portions of which
appear in the comma shape, much as in other spirilla--_e. g_., spirilla
undula, which do not always form complete spirals, but consist only of
more or less curved rods. The comma bacilli thrive well in meat infusion,
growing in it with great rapidity. By examining, microscopically, a drop
of this broth culture the baccilli are seen in active movement, swarming
at the margins of the drop, interspersed with the spiral threads, which
are also apparently mobile. They grow also in other fluids--_e. g_., very
abundantly in milk, without coagulating it or changing its appearance.
Also in blood serum they grow very richly.
Another good nutrient medium is gelatine, wherein the comma bacilli form
colonies of a perfectly characteristic kind, different from those of any
other form of bacteria. The colony when very young appears as a pale and
small spot, not completely spherical as other bacterial colonies in
gelatine are wont to be, but with a more or less irregular, protruding, or
jagged contour. It also very soon takes on a somewhat granular appearance.
As the colony increases, the granular character becomes more marked, until
it seems to be made up of highly refractile granules, like a mass of
particles of glass. In its further growth the gelatine is liquefied in the
vicinity of the colony, which at the same time sinks down deeper into the
gelatine mass, and makes a small thread-like excavation in the gelatine,
in the center of which the colony appears as a small white point. This
again is peculiar; it is never seen, at least so marked, with any other
bacterium. And a similar appearance is produced when gelatine is
inoculated with a pure culture of this bacillus, the gelatine liquefying
at the seat of inoculation, and the small colony continually enlarging;
but above it there occurs the excavated spot, like a bubble of air
floating over the bacillary colony. It gives the impression that the
bacillus growth not only liquefies the gelatine, but causes a rapid
evaporation of the fluid so formed. Many bacteria also have the power of
so liquefying gelatine with which they are inoculated, but never do they
produce such an excavation with the bladder-like cavity on the surface.
Another peculiarity was the slowness with which the gelatine liquefied,
and the narrow limits of this liquefaction in the case of a gelatine disk.
Cultures of the comma bacillus were also made in agar-agar jelly, which is
not liquefied by them. On potato these bacilli grow like those of
glanders, forming a grayish-brown layer on the surface. The comma bacilli
thrive best at temperatures between 30° and 40° C., but they are not very
sensitive to low temperatures, their growth not being prevented until 17°
or 16° C. is reached. In this respect they agree with anthrax bacilli.
Koch made an experiment to ascertain whether a very low temperature not
merely checked development but killed them, and subjected the comma
bacilli to a temperature of 10° C. They were then completely frozen, but
yet retained vitality, growing in gelatine afterward. Other experiments,
by excluding air from the gelatine cultures, or placing them under an
exhausted bell jar, or in an atmosphere of carbonic acid, went to prove
that they required air and oxygen for their growth; but the deprivation
did not kill them, since on removing them from these conditions they again
began to grow.
The growth of these bacilli is exceptionally rapid, quickly attaining its
height, and after a brief stationary period as quickly terminating. The
dying bacilli lose their shape, sometimes appearing shriveled, sometimes
swollen, and then staining very slightly or not at all. The special
features of their vegetation are best seen when substances which also
contain other forms of bacteria are taken--_e. g_., the intestinal
contents or choleraic evacuations mixed with moistened earth or linen and
kept damp. The comma bacilli in these conditions multiply with great
rapidity so as to far outnumber the other forms of bacteria, which at
first might have been in far greater abundance. This state of affairs does
not last long; in two or three days the comma bacilli began to die off,
and the other bacteria began to multiply. Precisely the same thing takes
place in the intestine, where, after the rapid initial vegetation is over,
and when exudation of blood occurs in the bowel, the comma bacilli
disappear and putrefactive bacteria predominate. Whether the occurrence of
putrefaction is inimical to the comma bacilli has not been proved, but
from analogy it is very probable. At any rate, it is important to know
this for certain, for if it be so, then the comma bacilli will not thrive
in a cesspit, and then further disinfection would be unnecessary. These
bacilli thrive best in fluids containing a certain amount of nutriment.
Experiments have not yet shown the limits in this respect, but Koch has
found them capable of growing in meat broth diluted ten times.
Again, if the nutrient medium become acid in reaction their growth is
checked, at least in gelatine and meat infusion; but singularly enough,
they continue to grow on the surface of a boiled potato which has become
acid, showing that all acids are not equally obnoxious to them. But here,
as with other substances which hinder their growth, they do not kill the
bacilli. Davaine has shown that iodine is a strong bactericide. He
experimented with anthrax bacilli in water to which iodine was added, and
the bacilli were destroyed. But practically the organisms have to be dealt
with in the alkaline contents of the bowel, or in the blood or fluids of
the tissues, where iodine cannot remain in the free state. Koch found that
the addition of an aqueous solution of iodine (1 in 4,000) to meat
infusion, in the proportion of 1 in 10, did not in the least interfere
with the growth of the bacilli in that medium. He did not pursue this line
of inquiry, seeing that in practice larger quantities of iodine than that
could not be given. Alcohol first checks the development of the comma
bacilli when it is mixed with the nutrient fluid in the proportion of 1 in
10, a degree of concentration which renders it impracticable for
treatment. Common salt was added to the extent of 2 per cent. without
influencing the growth of the bacilli. Sulphate of iron, in the proportion
of 2 per cent., checks this growth, probably by precipitating albumimites
from the fluids, and possibly also by its acid reaction; certainly it does
not seem to have any specific disinfecting action--i.e., in destroying the
bacilli. Indeed, Koch thinks that the admixture of sulphate of iron with
fæcal matter may arrest putrefaction, and really remove what may be the
most destructive process to the comma bacilli. Hence he would distinguish
between substances which merely arrest putrefaction and those which are
bactericidal; for the former may simply serve the purpose of preserving
the infective virus. Among other substances which prevent the growth of
the comma bacilli may be mentioned alum, in solutions of the strength of 1
in 100; camphor, 1 in 300; carbolic acid, 1 in 400; oil of peppermint, 1
in 2,000; sulphate of copper, 1 in 2,500 (a remedy much employed, but how
much would really be needed merely to hinder the growth of the bacilli in
the intestine!); quinine, 1 in 5,000; and sublimate, 1 in 100,000. In
contrast with the foregoing measures for preventing the growth of these
bacilli is the striking fact that they are readily killed by drying. This
fact is proved by merely drying a small drop of material containing the
bacilli on a cover-glass, and then placing this over some of the fluid on
a glass slide. With anthrax bacilli vitality is retained for nearly a
week; whereas, the comma bacillus appears to be killed in a very short
time. Thus it was found that although vitality was retained--depending
largely upon the number of bacilli--for a short time, yet withdrawal of
the nutrient fluid for an hour or even less often sufficed; and it never
happened that the bacilli retained vitality after a deprivation lasting
twenty-four hours. These results would seem to point to the fact that the
comma bacillus does not, like the organisms of anthrax and vaccinia, pass
into the resting state (Daner-zustande) by drying; and if so, it is one of
the most important facts in the etiology of cholera. Much, however,
remains to be done, especially with regard to the soiled linen of cholera
patients being kept in a damp state. He found that in soiled articles,
when dried for a time, varying from twenty-four hours and upward, the
comma bacilli were quite destroyed. Nor was the destruction delayed by
placing choleraic excreta in or upon earth, dry or moist, or mixed with
stagnant water. In gelatine cultures the comma bacilli can be cultivated
for six weeks, and also in blood serum, milk, and potato, where anthrax
bacilli rapidly form spores. But a resting state of the comma bacilli has
never been met with--a very exceptional thing in the case of bacilli, and
another reason why the organism must be regarded rather as a spirillum
than a bacillus, for the spirilla require only a fluid medium, and do not,
like the anthrax bacilli, thrive in a dry state. It is quite unlikely that
a resting state of the comma bacillus will ever be discovered; and,
moreover, its absence harmonizes with our knowledge of cholera
etiology.--_The Lancet_.
* * * * *
[THE MEDICAL RECORD.]
MALARIA.--THE NATURAL PRODUCTION OF MALARIA, AND THE MEANS OF MAKING
MALARIAL COUNTRIES HEALTHIER.
[Footnote: An Address delivered at the Eighth Session of the International
Medical Congress, Copenhagen, August 12, 1884.]
By Conrad Tommasi Crudeli, M.D., Professor of Hygiene, University of Rome,
Italy.
Before entering upon my subject, I must crave the indulgence of those of
my colleagues whose language I have borrowed for any italicisms that I may
use, as well as for the foreign accent which must strike their ears more
or less disagreeably. Desiring to respond as well as lay in my power to
the invitation with which I have been honored to discuss the hygienic
questions relating to malaria, I have chosen the French language as being
the one in which, apart from my mother tongue, I could express myself with
the greatest ease and precision.
I shall be pardoned also, I hope, for having employed the terms "malaria"
and "malarial districts" in place of the more commonly used expressions
"paludal miasm" (_miasme paludeen_) and "marshy regions" (_contrées
marécageuses_). The substitution is not a happy one from a literary point
of view, but I have made it deliberately and for the following reason: The
idea that intermittent and pernicious fevers are engendered by putrid
emanations from swamps and marshes is one of those semi-scientific
assumptions which have contributed most to lead astray the investigations
of scientists and the work of public administrations. This idea, so
widespread and so well established by the traditions of the school, is
radically false. The specific ferment which engenders those fevers by its
accumulation in the atmosphere which we breathe is not exclusively of
paludal origin, and still less is it a product of putrefaction. Indeed, in
every region of the globe between the two Arctic circles there are swamps
and marshes, steeping-tanks of hemp and flax, large deltas where salt and
fresh waters mix, and yet there is no malaria there, although putrid
decomposition is on every side. On the other hand, in the same parts of
the globe there are places which are not and never were marshy, and in
which there is not the least trace of putrefaction, but which,
nevertheless, produce malaria in abundance. I reject, therefore, wholly
the paludal assumption, and in order to express this view in the title of
my paper, have been forced to employ terms which to my hearers may sound
like italicisms.
The Italians generally have 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. Rica does not hesitate
to admit that when a swampy tract is heated by the sun's rays to the
necessary point for the putrid decomposition of the organic matters
contained in it, the "chemical ferment," or rather the "mephitic gases,"
to which is attributed the morbific action, are developed, whatever may be
the distance from the equator at which this marshy region lies. But since
it has been ascertained that malaria is produced in soils of the most
varied chemical composition, _the persistent identity of this product_ has
become chemically inexplicable; while it is however readily conceivable,
if one admits that malaria is an organized ferment which easily finds the
necessary conditions for its life and multiplication in the most varied
soils, as is the case with millions of other organisms vastly superior to
the rudimentary vegetables which constitute the living ferments.
The same thing may be said of _the progressive intensity of the morbific
production in abandoned malarious districts_. This fact has been
historically proved in several parts of the earth, and especially in
Italy. A large number of Grecian, Etruscan, and Latin cities, even Rome
itself, sprang up in malarious territories and attained a high state of
prosperity. First among the reasons for this success must be placed the
works undertaken with a view of rendering these places more salubrious,
and which lessened the evil production, _but almost never extinguished it
completely_. After the abandonment of these localities, the production of
malaria recommenced in a degree which went on increasing from age to age,
and which has rendered some of these places actually uninhabitable. This
was seen, in the time of the ancient Romans, in Etruria, when it was
conquered and laid waste, and in several parts of Magna Græcia, and of
Sicily. From the fall of Rome even to the present day, this phenomenon has
been manifested in a very evident manner in the Roman Campagna, in certain
parts of which, even up to the time of the Renaissance, it was possible to
maintain pleasure houses, but which are now unhabitable during the hot
season. In many cases the physical conditions of the soil have undergone
no appreciable change during centuries, so that it is impossible to
attribute so enormous an augmentation of malaria to an increase in its
annual production, itself increased by a progressive alteration of the
chemical composition of the soil. But if, on the contrary, it be admitted
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 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°C.
(67.5°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 (_comblées_). 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, _à 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.