ON THE PRESUMED SOURCES OF MALARIA.
§ 1. For all practical purposes, the fevers termed intermittent
and remittent may be held to have their origin in one cause. Thus,
whether on the marshy coasts of Essex and Kent, or the more dreadful
banks of the Gambia and Niger, it is not improbable that the fever
so destructive to European life is of one character--mild in Essex;
fatal in Sierra Leone. But the fact is not to be overlooked, that when
fever assumes an intermittent character, however it may conduce to the
inefficiency of the population, it does not greatly swell the bills of
mortality; on the other hand, the remittent form of fever constitutes
that grand and hitherto insurmountable obstacle which Nature seems to
have placed to the extension of the white man over the earth, excluding
him, seemingly for ever, from the tropical regions of the world.
A favourite theory with medical men was, that the evil influence which
causes fever, whether in Essex or on the Gambia, by the Scheld or the
Niger, was a certain miasma produced by marshes more or less remote
from human abodes; sometimes it was maintained that to produce the
miasma these marshes must be in a great measure dried up, or in the
process of being so; at other times an opposite opinion was held. These
hypotheses were refuted, or at least much shaken, by Major Tulloch,
in his invaluable “Statistical Report on the Sickness, Mortality, and
Invaliding among Troops on the Western Coast of Africa” (p. 26). “So
long as the fever continued to make its appearance during the rainy
season, excessive moisture was deemed one of the principal causes,
but that theory has been abandoned since it has, on three or four
occasions, appeared and raged with equal violence in the middle of
the dry season. If we attempt to connect it with temperature, the
range of the thermometer offers equally contradictory results, the
disease having originated and prevailed nearly as often when that
was at the minimum as when at the maximum. Variations in atmospheric
pressure afford no clue whatever to the solution of the difficulty, for
here, as in all tropical climates, the fluctuations of the barometer
are exceedingly slight. No definite connexion has ever been traced
between the prevalence of any particular wind and the outbreak of
the disease; the breeze blows over the same district in the healthy
as in the unhealthy season. Besides, it seems entirely to negative
the supposition that any of these can be more, perhaps, than mere
accessories, when we find, from 1830 to 1836, the colony of Sierra
Leone remarkably free from fever, without any perceptible change
in these respects. It does not appear that the composition of the
atmosphere during the prevalence of yellow fever in this command has
ever been examined, to ascertain if it differed from what has usually
been observed at periods comparatively healthy; but this test has been
applied without any satisfactory result in other countries. Unless some
light, therefore, can be thrown on the subject by a careful examination
of the electrical state of the atmosphere at such periods, there seems
little hope of the origin of this disease being ever distinctly traced
to any appreciable agency--a circumstance which, except as regards the
interests of science, is perhaps of less importance, since where the
cause is so exceedingly subtle it would, even if discovered, be in all
probability beyond human control.”[21]
[21] “Statistical Report on the Sickness, Mortality, and Invaliding
among the Troops in the West Indies.” Prepared from the Records of
the Army Medical Department and War-Office Returns. London, 1838. It
has been objected to these Reports that they embrace only one class
of lives. But this does not diminish their value, for the lives they
report on are presumed to be the selected lives of men in the prime
of life.
In corroboration of the same views, amounting in fact to a rejection
of the favourite hypothesis of the professors of the healing
art--namely, that this fever originated in the miasma of marshes
near the station, this careful and honest observer, whose merits as
such have subsequently been fully tested in the celebrated Crimean
inquiry, makes this further remark:--“The hypothesis that this fever
originates from the miasma of marshes in the immediate vicinity of
the station, as elsewhere it has been supposed to do, is directly
opposed to the fact of the Isles de Loss, Acera, and the peninsula
of Sierra Leone itself, being so subject to it, though all are in a
certain degree remote from the operation of any such agency. If it
be referred to similar exhalations wafted to the distance of several
miles, how is its prevalence to be accounted for at Fernando Po, a
mountainous region, and bordering on a mainland still more so, and
where, so far as can be ascertained, no such agency is in operation?
Instances of disease having raged with the same violence on the rocky
Isles de Loss and the sandy wastes of Senegal, as in those parts of the
coasts where vegetation is most dense, preclude the likelihood of it
originating in a superabundance of that agency. In every description
of situation along the coast has this scourge of Europeans been
found to prevail. The low, swampy Gambia, the barren Isles de Loss,
the beautifully-diversified features of Sierra Leone, the open and
park-like territory around Acera, the lone, jungle-covered hills of
Cape Coast Castle, and the rugged, mountainous island of Fernando Po,
however different in aspect, have all exhibited the same remarkable
uniformity in giving birth to the disease.”
It may, indeed, be objected that the fevers of Western Africa differ
essentially from those traceable to the deltas of rivers, and to the
lowlands alternately inundated and exposed to a high temperature, of
more temperate climates; but I see no good reason in favour of such an
opinion. The tables of sickness and mortality distinctly state that
the fevers were intermittents and remittents, but mainly remittents,
and that continued or ardent fever was scarcely present; whilst in
Canada precisely the reverse is the case, intermittents prevailing to
a great extent, remittents being comparatively rare. It would seem,
however, that whether or not these fevers spring from a common cause,
the temperature of the locality greatly influences the character of the
disease.
It is impossible to deny the influence humidity has in engendering
malarious tendencies, but it is not necessary that the humidity be to
any great extent. Water is essential to life, it is essential also to
the production of fermentation, of putrefaction; the absolute desert,
as I have already remarked, is always healthy; so is the surface of
the great ocean, which although it abounds with life, never putrefies,
never exhales unpleasant odours. Countries, like some districts of
Southern Africa and of Australia, where it seldom rains, are the
healthiest countries in the world; there fevers of all types are nearly
unknown, and the sufferers from such coming from unhealthy climates,
recover speedily from the sad condition to which a residence in a
tropical country and frequent attacks of fever may have reduced them.
The Royal African Regiment, composed mainly of deserters, left the west
coast of Africa for the Cape of Good Hope in 1817; many of them were so
reduced in health as to be obviously unfit for service in any country
where fevers of an intermittent or remittent character prevailed.
Now, a residence on the frontiers of the colony of the Cape not only
cured these fevers, but seems also to have been equal to the removal
of those sequelæ of fever and dysentery which haunt those who have
greatly suffered from them, bringing them in the end to an untimely
grave. Nothing of the kind occurred in this remarkable country; all, or
nearly all, recovered, and the mortality and sickness of this shattered
corps, removed from Sierra Leone and the Gambia to the frontier
districts of the Cape of Good Hope, fell considerably below what it is
amongst the same class in Britain. These facts merit the attention of
all interested in the welfare of the army of Britain, an army exposed
more than any other to the effects of climate in all regions of the
world.[22]
[22] The army of England is, and perhaps has at all times been, an
aggressive army, maintained to intimidate foreign races and nations.
It resembles in many of its main features the army of ancient
Carthage.
§ 2. The statistics I have just referred to may seem to some to shake
all modern theories of malaria that have ever yet been offered to the
public. I admit this to be the case; but I trust to be able to show
that in the remains of animal and vegetable life, elements collected
in the greatest abundance by the banks of rivers and lakes in marshy
countries, near shores alternately exposed and covered by the tide, and
especially in tidal rivers, but not exclusively in such localities, we
have the source of that poison whose terrible effects on human life
need not be enumerated here.
The result of Major Tulloch’s report in regard to the relative
prevalence at different stations in British America of remittent and
intermittent fevers, shows in a still stronger light the difficulty
of establishing any uniform connexion between the presence of marshy
ground and the existence of these febrile diseases, to which the
exhalations from it are supposed to give rise; but they do not
refute the view I take,[23] which is based on the researches of the
profoundest chemists. As it was formerly shown that in some of the
Ionian Islands, totally destitute of marsh and comparatively barren
of vegetation, more remittent and intermittent fevers have been under
treatment among the troops, than in others where these alleged sources
of disease existed in the greatest abundance; so in the present Report
we find it established, that yellow fever of the most aggravated form
has repeatedly made its appearance in Ireland Island in the Bermudas, a
rocky barren spot only a few hundred yards in breadth, “containing no
marsh, and with little or no vegetation except a few cedar trees.”
[23] Report: Section, Mediterranean.
“Conversely, again, we find that these diseases prevail to a remarkable
extent along the banks of the lakes and the margin of the streams in
Upper Canada, while they are comparatively rare in similar situations
in the Lower Province; that among the troops at Fredericton, living on
the marshy banks of a river, surrounded by a dense vegetation, scarcely
a case of them is ever known; and that a similar exemption is enjoyed
even by those at Annapolis and Windsor in Nova Scotia, though quartered
at the _embouchure_ of rivers daily subject to extensive inundations,
and of which the banks, for the distance of several miles, exhibit that
combination of mud, marsh, and decayed vegetation which is generally
supposed a most prolific source of such diseases.
“When in subsequent reports we come to investigate the operation of
these diseases on the west coast of Africa and other colonies, we shall
be able to adduce still more satisfactory evidence on this subject;
in the meantime we have felt it our duty to place the preceding facts
in a prominent point of view, not for the purpose of establishing any
particular theory, but to show how inadequate in many instances is
the supposed influence of emanations from a marshy soil to account
for the origin of these diseases. All the evidence obtained seems
only to warrant the inference that a morbific agency of some kind
is occasionally present in the atmosphere, which, under certain
circumstances, gives rise to fevers of the remittent and intermittent
type; and that though the vicinity of marshy and swampy ground appears
to favour the development of that agency, it does not necessarily
prevail in such localities, nor are they by any means essential either
to its existence or operation.
“Notwithstanding the doubt in which this branch of the investigation
is still involved, we may venture, from the facts adduced in all the
reports hitherto submitted, also to draw the conclusion, that when
this morbific agency manifests itself in the epidemic form, its
influence is frequently confined to so limited a space as to afford a
fair prospect of securing the troops from its ravages by removing to a
short distance from the locality where it originated. The history of
the epidemic fevers at Gibraltar furnishes several remarkable instances
of this kind, and we have also shown that, both in the West Indies and
Ionian Islands, one station has frequently suffered to a great extent
from yellow fever, while others within the distance of a few miles have
been entirely exempt.
“In the epidemic cholera at Montreal and Halifax, which seems to have
been in this respect somewhat analogous in its operation, we have also
had occasion to remark the sudden cessation of the disease immediately
on the removal of the troops to a short distance.”[24]
[24] It may be asked, Why not inquire into the statistics of fever
in Essex? The truth is, that no such exist. The conjectures and
recollections of civil practitioners are valueless.
The discordance prevailing between observers, equally honest, equally
intelligent, arises, no doubt, from this, that all the elements of
the problem to be solved are not yet discovered; nor could this be
expected until a refined chemistry had more fully developed the
relation between chemical and physiological phenomena. The very
essence of the affinities between the soil and vegetable and animal
life was a complete mystery until lately, whilst the relations of the
superambient atmosphere to the organic remains of what had ceased
to live, were wholly misunderstood. The cause of the potato blight,
which produced a famine in Ireland, is still a mystery; so also is
that of the vine. A disease very fatal to horses, called Paard-sick,
from its only attacking the horse, is endemic in some districts of
the Cape; that is, in the healthiest country in the world. The nature
of the Paard-sick has never been discovered. It spares the _wilde_ of
the horse genus--the quagga, zebra, &c.--but is fatal to the domestic
breed. Man’s interference, then, proves at times fatal to his protegée.
It is everywhere the same, unless his interference be guided by all the
lights which the highest reasoning powers, the shrewdest observation,
and oft-repeated experience can afford. The two Canadas are in an
especial manner the land of rivers, lakes, marshy forests, swampy
meadows, and a soil into which the plough never penetrated until the
white man appeared. As a natural result, it might be conjectured and
presumed that intermittents and remittents, under at least certain
of their forms, would be equally frequent and universally diffused.
Statistics prove it to be directly the reverse, Upper Canada being to
Lower Canada, in respect of these fevers, as 178 intermittents is to
26 remittents; whilst even of these 26 it is affirmed that the greater
number of them came from the Upper Province. To show that I do not
exaggerate this singular fact, I quote the remarkable statistics of
Major Tulloch.
“Taking the results of these ten years as the basis of our deductions,
then, the prevalence of intermittent fevers in Upper compared with
Lower Canada is as 178 to 26. It is necessary, however, to keep in
view that all the admissions (amounting only to 26) from intermittent
fever in Lower Canada did not originate there, by far the greater
proportion of them having occurred among soldiers who came from the
Upper Province while labouring under that disease, or who had acquired
a predisposition to it during a previous residence there. Indeed,
except at Isle aux Naix and the other small stations along the banks
of the Richelieu, fevers of the intermittent type are rarely indigenous
in Lower Canada; at Quebec they are said to be unknown, and at Montreal
nearly so.
“In Upper Canada these diseases prevail most among the troops stationed
along the course of the great lakes from Kingston to Amherstberg, they
are almost unknown at Penetanguishene and By Town. The settlers who
reside even at the distance of a few miles inland rarely suffer from
them; yet the districts enjoying this exemption are in many parts
covered with lakes, intersected by streams, and abound in marshy
ground, decayed vegetation, and all the other agencies to which the
origin of this type of fever is generally attributed. A reference to
the report on Nova Scotia and New Brunswick will also show that though
the same agencies exist to a similar extent at some of the stations in
that command, intermittent fevers are almost unknown.
“These diseases, too, are said to be comparatively rare wherever the
surface is covered with dense forests, even though the ground is wet
and marshy. The vicinity of lands recently cleared is most subject
to them, particularly meadows or open patches of the forest, which,
though denuded of trees, have not been brought under cultivation.
It would appear, too, that their prevalence is diminishing with the
progress of agricultural improvement; for it will be observed, on
reference to the Abstract of Diseases, No. III. of Appendix, that since
1831--a period during which this province has been rapidly advancing
in wealth and population, and many important changes have taken place
in the vicinity and stations occupied by the troops--intermittents
have become comparatively rare, the proportion attacked having been
scarcely one-tenth part so high as the average previous to that
period. Intermittents most frequently occur from July to September,
when a high temperature prevails; but they are also to be met with,
though more rarely, in spring, when that agency could only operate
in a trifling degree to induce them. Though a source of inefficiency
among the troops, they add but little to the mortality, as not one
case in a thousand proves fatal. A person who has been once attacked
is exceedingly apt to suffer from them again; but this susceptibility
is easily removed by change of residence to the northern parts of the
province, or to Lower Canada.
“In some years, fever also manifests itself along the borders of the
lakes in the remittent form, but not of so fatal a character as in the
West Indies or the Mediterranean; for only one case in sixteen is found
to have proved fatal among the troops.
“The febrile diseases of Upper Canada are by no means uniform in their
prevalence. Even in years when the degree of temperature, fall of
rain, or extent of vegetation have been much the same, the proportion
of cases, particularly of intermittents, is very different. A general
impression exists, that their prevalence is in some measure dependent
on the height of the waters in Lake Ontario, which attain their maximum
in June or July. If, from the quantity of snow or moisture in the
course of the year, this is found to be greater than usual, febrile
diseases are expected to abound, and the reverse if the maximum has
been under the average. As Lake Ontario is the reservoir into which all
the waters of Upper Canada are drained off before finding their way
to the ocean, this theory, if accurately substantiated, would tend to
show how far the origin of these diseases depended on moisture, and we
therefore instituted the following comparison between the height of
the waters in the lake, as measured at Kingston for a series of years,
and the prevalence of fever in Upper Canada during the same period:
+-----------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
| |1818.|1819.|1820.|1821.|1822.|1823.|1824.|1825.|1826.|1827.|1828.|
+-----------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
|Average height of| | | | | | | | | | | |
|lake in Kingston | | | | | | | | | | | |
|Harbour in each | 14 9| 13 3| 12 3|11 11| 12 1| 13 5|13 11| 12 5|12 10| 14 3| 15 7|
|year | | | | | | | | | | | |
|(feet and inches)| | | | | | | | | | | |
+-----------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
|Cases of inter- | | | | | | | | | | | |
|mittent fever | 110 | 319 | 509 | 348 | 222 | 143 | 171 | 135 | 111 | 220 | 489 |
|in Upper Canada | | | | | | | | | | | |
+-----------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
|Cases of other | 109 | 54 | 150 | 152 | 132 | 69 | 168 | 190 | 155 | 185 | 300 |
|fevers | | | | | | | | | | | |
+-----------------+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+-----+
“Here we find that, though in the last of these years the maximum
height of water in the lake happened to correspond with the greatest
prevalence of fever, the latter can by no means be looked upon as a
consequence of, or in any way connected with, the former; since in
1818, when the water rose to within a few inches of the same level,
there was less fever than in any of the years under observation;
whereas in 1820 and 1821, when the waters of the lake appear to have
been at the minimum, there was more than in any of the years prior to
1828.
“This supposition seems to have originated in the circumstance of
fevers being generally most prevalent from June to October, which
happens to correspond with the period when the waters of the lake
are at the greatest height; but the wide sphere over which these
statistical investigations now extend, has enabled us to show that
febrile diseases always prevail most at that season of the year, even
in countries where no such cause is in operation to produce them;
consequently, the rise of the waters in the lakes can no more be
regarded as the cause of fever in America, than the cessation of the
trade winds about the same period can be deemed a satisfactory reason
for the appearance of that disease in the West Indies. Both are merely
coincidences which, by those who have not a sufficiently extensive
field of observation, are apt to be mistaken for causes.”
There arises out of all such inquiries one obvious deduction--viz.,
that the essential nature of malaria is altogether unknown; and that
unless we choose to remain contented with such vague hypotheses as
those of Macculloch, now adopted by the Medical Board of Health of
Great Britain,[25] other inquiries must be entered on. The assertion
is as easily made as its refutation is difficult, that typhus fever is
caused by a neglected drain or ditch; that scarlet fever, small-pox,
and cholera have for their origin the same cause; that if they do not
immediately produce the poison, they predispose the human frame for
its reception; and that as a necessary result, all such diseases,
and deaths resulting therefrom, and from zymotic forms of disease
generally, are preventible by human agency. Let us leave these Utopian
views to the clever pens skilled in the art of making that seem new
which is not new, and that seem true which is not true, and patiently
inquire into some of the many difficulties besetting all investigations
into Nature’s processes, and man’s interpretation of them.[26]
[25] As by the Registrar-General: see his Reports.
[26] The ancient Egyptians seem to me to have long ago settled this
question, practically. On the subsidence of the Nile they, without a
day’s delay, commenced agricultural operations; nothing was allowed
to fall into rottenness or putrefaction.