THE RELATION BETWEEN EPIDEMIC AND ENDEMIC DISEASES.
Epidemic diseases, which multiply their germs in any climate, and under
apparently the most varying conditions of temperature and hygrometric and
electrical states of atmosphere, offer many points of contrast with Endemic
affections, and many of relationship. The latter are traceable to a certain
extent, to geological and geographical positions of the localities where
they are observed to prevail, in combination with atmospheric vicissitudes
and peculiarities, as well as to extent of cultivation of the soil: it has
been remarked that the sickly island (as it is called) of St. Lucia has
certain salubrious parts, but these are where sulphur abounds; this
geological peculiarity has been deemed sufficient to account for the
absence of endemic affections in these parts, and with much force of
reason; for in the neighbourhoods where sulphur or sulphurous acid, a
compound of sulphur, is an element prevalent in the soil or atmosphere,
vegetation and the ague disappear together.
Now ague, and other endemic fevers, doubtless originate from some allied,
if not identical cause; for the localities in which they appear have so
many {97} features in common, that we are constrained to acknowledge that
endemic fevers have some relations and analogies, though not yet
unravelled.
Geographical situation, together with certain vegetation, particularly of
grounds which grow rice, is one remarkable for the production of endemic
affections. But the soil which generates or gives force to the
contaminating matter, is not alone the part where human beings feel its
influence most severely. A low marshy ground, prolific of malaria, may be
comparatively free; while some neighbouring elevated land, to which
prevailing currents of air waft the volatile elements of disease, may be
desolated by their virulent and concentrated action. "Malaria may be
conveyed a considerable distance from its source, _and be condensed_ in the
exhaled vapour, when attracted by hills or acclivities in the vicinity, and
when there are no high trees or woods to confine it, or to intercept it in
its passage."
The inhabitants of the city of Abydos were at one time subject to disease,
arising from malaria, generated in some neighbouring marshes; by draining
these marshes, which suspended the growth of rank vegetation, the city
became healthy.
Rome is in like manner even now subject to fevers, having a similar origin.
Sir James Clark says, "Among the more prevalent diseases of Rome, malaria
fevers are the most remarkable, and claim our first notice." He considers
the fevers to be of exactly the same nature as those of Lincolnshire {98}
and Essex in this country, of Holland, and certain districts over the
greater part of the globe. To the climate, the season, or the concentration
of the cause of these fevers, he attributes their varieties. It is the same
disease, he says, whether from the swamps of Walcheren, or the pestilential
shores of Africa.
From July to October the inhabitants of Rome are most subject to these
affections.
Sir James Clark further says: "It may be stated as a general rule, that
houses in confined shaded situations, with damp courts or gardens, or
standing water close to them, are unhealthy in every climate and season;
but especially in a country subject to intermittent fevers, and during
summer and autumn. The exemption of the central parts of a large town from
these fevers, is explained by the dryness of the atmosphere, and by the
comparative equality of temperature which prevails there."
In this respect there is a marked difference between an epidemic and an
endemic affection; for when an epidemic disease attacks a city or town we
do not discover that the central parts are more exempt than others; indeed,
it is rather the contrary; for the most crowded parts of towns and cities
are those, if not exactly in the centre, which would be comprised in a
space nearer to the centre than the circumference; and it has been in those
parts generally where the epidemic influences seem to have exercised the
most potent sway. One would more naturally suppose, that a city surrounded
by {99} paludal miasm, and not itself being capable of generating the
poison, should be more affected at the circumference, from the simple fact
that the paludal germs, which rise in the air, are suspended in the fogs
and dews of the atmosphere. These, unless widely dispersed by the winds,
would remain within a comparatively confined space; and those situations
nearest to them would be most subject to their influence. Besides, it has
been shewn, that a small wood or hill, or even a wall, has been sufficient
to cut off or obstruct the paludal miasm.
Without enumerating all the known endemic diseases, two or three may be
alluded to for our present purpose; viz. that of shewing that endemic and
epidemic diseases have a similar origin.[39]
It is well known that under certain favouring conditions an endemic may
become a malignant and pestilential disease; that Yellow Fever, which is
always endemic in the west, Cholera in the east, and the Plague in the
south of Europe and north of Africa, every few years takes on an epidemic
form, and desolates considerable tracts of country.[39]
The Pestilence which raged in the summer and autumn of 1804 in Spain,
commenced at Malaga, and remained for a considerable time confined to its
{100} boundaries, in consequence of the measures of precaution that were
used, in preventing all communication between the inhabitants of the
infected city and those living in the surrounding country. It was only in
consequence of persons escaping through the cordon, and passing into the
interior of the country, that the disease spread, and extended its ravages
to distant places.
It appears to be quite clear, that this disease may properly be considered
in the first instance of endemic origin; but the tendencies, atmospheric
and otherwise, were such as to favour its multiplication in other districts
than that in which it first came into active existence. From this we may
infer, that the seeds of the disease were dormant, and only became roused
into vital activity by fortuitous circumstances. Dr. Rush states, that the
endemic disorders of Pennsylvania were converted, by clearing the soil, to
bilious and malignant remittents, and to destructive epidemics. Dr. Copland
says, it has been observed, especially in warm climates, and in hot seasons
in temperate countries, that when the air has been long undisturbed by high
winds and thunder-storms, and at the same time hot and moist, endemic
diseases have assumed a very severe and even epidemic character.
Dr. Robertson also confirms this view. "Endemic diseases, in cases of
neglect and preposterous management, are found to become more malignant
even in the most temperate climates; and to {101} generate a matter in
their course, capable of producing a particular disease in any
circumstances. _Indeed the origin of every_ contagious fever unattended
with eruptions, with the exception of Plague, must commence in this way."
Why Dr. Robertson should except eruptive Fevers and Plague I cannot
understand, for they must have had a commencement; and their many points of
similarity indicate, if not an identical, an analogous source to other
endemic fevers.
It will doubtless be generally acknowledged that endemic and epidemic
diseases depend upon some unknown agents, having their source in malarious
districts, and being capable of assuming either a contagious or
non-contagious character, according to circumstances.
If, therefore, we find that under any conditions an endemic affection
becomes capable of being propagated by contagion, the same law will hold
with regard to it as to the Plague; that the power of reproduction in this
matter is evidence of life, according to the doctrine laid down in the
earlier part of this work. But whether or not infection be admitted, a
matter generated in a malarious district, if confined in its effects to
that district alone, would not necessarily imply an inorganic nature of the
poison; for it is difficult to understand how inorganic poison, prevailing
generally over a certain tract of country, could select particular
individuals for its victims. If chloroform, chlorine, carbonic acid,
sulphuretted hydrogen, or even spores of poisonous fungi, (as {102}
supposed by Mitchell, which, as he regards their effects, would act in a
similar manner to inorganic compounds) were the agents, all persons would
suffer more or less, and the majority be similarly affected. We do not find
that uniformity of symptoms, which attend upon the exhibition of poisons in
the ordinary acceptation of the term, poisoning. This subject shall be more
particularly considered, when treating of the influence of organic germs on
animals and plants.
The history of the Eclair steamer is particularly interesting, as shewing
the extraordinary tenacity with which the germs of disease attach
themselves to vessels, which we may call floating houses.
The crew of the Eclair contracted Yellow Fever on the coast of Africa, and
a number of them died. The remainder, sick and well, landed at Bona Vista,
one of the Cape de Verde Islands, and the vessel underwent a process of
washing, whitewashing, and fumigating. Nevertheless, on the return of the
ship's company, the disease broke out again with equal intensity, and the
vessel was ordered home. Sixty-five out of 146 officers and men, who
composed the crew, died of the disease before reaching Portsmouth, and
twenty-three were sick at the time of arrival.
Eight days after the Eclair left Bona Vista, a Portuguese soldier who had
mixed with her crew died in the fort which had been occupied by them. Other
soldiers then fell sick, and the fort was abandoned. The fever still
spread.
From the 20th September, when the first soldier {103} was attacked, to the
first week in December, the fever continued to rage, and at that period it
had found its way into almost all the country villages. The fever was
believed to be the genuine black vomit fever; it proved contagious almost
without exception to the nurses of the sick.
This is an abstract of Mr. Rendell's letter to Lord Aberdeen, Mr. Rendell
being British Consul at Bona Vista.
Now at the time the fever broke out in the island the weather was
extraordinarily hot, and much rain had fallen, and the town itself was
badly drained and in a filthy state; can it be imagined then that the seeds
of a disease liable to assume a pestilential character should lie dormant
or be annihilated under circumstances the most favourable for their
development, especially when we know that endemic diseases may assume a
malignant character?
This is just one of many cases which confirm our opinion in this respect,
that plants and diseases are not long in making their appearance where the
soil and atmosphere are congenial.
The tenacity with which the disease attached itself to the Eclair is
sufficiently explained in the absence of due ventilation; in fact, that in
the first instance there was no ventilation at all in the hold of the ship.
This also the more readily affords a clue to the disaster through all its
stages, first in the contraction of the disease as an endemical affection
in the vessel; secondly, in the multiplication of the {104} germs in the
damp ill-ventilated hold, in a warm climate; and thirdly, the persistence
and entire localization of the disease to the vessel when it arrived in the
climate of the British shores; while, fourth and lastly, in the unusually
hot and damp island of Bona Vista, the seeds of the disease were sown, and,
as we might expect, multiplied indefinitely.
The consecutive attacks of the crew of the Eclair shew that here a noxious
gas or a vaporized inorganic poison could not have been the cause of the
disease, for as I have before said, in this case the attacks should have
been simultaneous; we find, on the contrary, that as the depressing effects
of the melancholy condition of the crew was almost hourly undermining the
health of the stoutest of them they as surely became the victims. The
Kroomen, or natives on board the ship had not suffered, shewing that they
were inured to the miasm, or were destitute of that condition of blood
which would be favourable to a propagation of the materies of the disease.
The Eclair we learn had left Bona Vista eight days when the first victim
breathed his last; this would give perhaps three or four days for the
incubation of the disease in the patient, or supposing he had not
contracted the germs of the disease before the crew of the Eclair left the
fort, some local favouring conditions were the means of keeping the germs
in a fertilizing state, for it is clear from this spot the infection spread
as from a centre or focus. {105} Such instances as these might be
multiplied to extend the length of the enquiry, but, I think, to little
advantage. The chief facts to be gathered are that an endemic affection
became epidemic and pestilential, contrary to its usual mode, for the
Portuguese official physician, on being consulted by the Governor of the
Island as to the safety of landing the contaminated crew, said, "No danger
at all; I have often brought sick men on shore coming in vessels from the
African coast, and I never knew any ill effects to arise." Putting the most
reasonable construction on this emphatic and straightforward language, we
may presume that ordinary, remittent, and yellow fever had been commonly
imported into the island, for it is not to be supposed but that both forms
of disease must have existed among those sick men who had "_often been
landed_," under the sanction of the Portuguese physician.
To take another instance; intermittent fever or ague, is a disease known
among almost all nations of the world, but it usually occurs in the endemic
form only. It is universally supposed to depend entirely upon marsh
effluvia, and we are accustomed to consider it as attaching only to low
lying countries;[40] but this is not always the case, for disease in {106}
this respect, like vegetation, may be found in various latitudes, to
accommodate itself at varying altitudes, to the temperature and climatic
relations, so as to appear indigenous. But though our prejudices are in
favour of a simple miasmatic source of ague, as its sole cause, there are
some who believe in its infectious nature. M. Sigaud, in his work on the
Climate and Diseases of Brazil, speaks of Epidemics of _grave intermittent
Fever_, and Dr. Copland says, that the epidemic prevalence of ague is a
better established fact than its infection, and has been admitted by most
writers.[41] We have, therefore, but to go one step further to arrive at
infection, after having found that an endemic disease under peculiar
circumstances, though but rarely, becomes {107} epidemic. The number of
persons attacked by ague in a malarious district, in proportion to the
population, is not so great as might be expected, considering that they are
always subject by night and day, more or less, to respire the air
containing the germs of intermittent fever; we might, therefore, deny the
paludal source of the affection, as reasonably as deny infection, if we
found that occasionally, persons, though subject to all the usual
influences, yet escaped all injurious consequences.
There are grades and varieties of infectious diseases, from the most
inveterate to the most mild and doubtful; but that all, without exception,
which can in any way be traced to a specific generating and organic cause,
may assume an exalted infectious character, and that the most inveterate,
on the contrary, may more resemble the mild and doubtfully infectious
forms, is a conviction that must be forced on all who pursue this enquiry
with unbiassed interest.
* * * * *
{108}
CHAPTER III.
THE REASONABLENESS OF THE APPLICATION OF THE FACTS TO THE INFERENCE.
--------
SECTION I.
THE CHEMICAL THEORY OF EPIDEMICS UNTENABLE.
It has been inferred that the germs of disease possess the property of
vitality, and a number of facts have been adduced to support the
proposition that vitality is the indwelling force by which the matter
generating epidemic and endemic disease exercises its influence over man
and animals. The reasonableness of the application of these facts to the
end in view has now to be considered. Chemistry cannot account for
epidemics.
Our first subject of reflection points to the chemical discoveries of the
last few years, and particularly to those of the great German chemist
Liebig. We find in the first paragraph of his Organic Chemistry applied to
Physiology and Pathology, the following words: "In the animal ovum, as well
as in the seed of the plant, we recognize a certain remarkable force, _the
source of growth_ or increase in the mass, _and of reproduction_ or of
supply of the matter consumed; a force in a state of rest. By the action of
external influences, by impregnation, by the presence of air and moisture,
the condition {109} of static equilibrium is disturbed. This force is
called the _vital force_, _vis vitae_, or vitality."
The doctrine of Liebig, that the vital force manifests itself in two
conditions, or rather, that it is known to be in two different states, that
of static equilibrium as in the seed, and in a dynamic state, as in that of
growth and reproduction, is perfectly applicable to the germs of disease;
the static equilibrium is referrible to the matter of vaccine lymph when
dried and preserved for use, and the dynamic forces of the matter are known
to be in operation during its reproduction and growth in the system of the
vaccinated child.
Then as to reproduction of matter by any chemical process, our author can
furnish us with no examples, for even in his explanation of the causes of
disease he is quite silent on this point, merely acknowledging that
diseased products must be either rendered "harmless, destroyed, or expelled
from the body." He further says, that "in all diseases where the formation
of contagious matter and of exanthemata is accompanied by fever, two
diseased conditions simultaneously exist, and two processes are
simultaneously completed," and that it is by means of the blood as a
carrier of oxygen that neutralization or equilibrium is established. Liebig
thus admits that an agent exists in the blood, capable of deteriorating it
at the expense of the oxygen, which he maintains is contained in the red
globules; he further acknowledges that two processes of diseased {110}
action are going on at the same time, and though he does not explain them,
I imagine him to mean that new contagious matter is generated and
eliminated from the blood, and that at the same time, there is that
condition of body which he would call simply a diseased state, and
characterizes it thus: "Disease occurs when the sum of vital force which
tends to neutralize all causes of disturbance, (in other words, when the
resistance offered by the vital force) is weaker than the acting cause of
the disturbance."
If I rightly apprehend his notions, they perfectly harmonize with my ideas,
to a certain extent, on the subject. They accord, at any rate, most
completely with the theory attempted to be established, and fully confirm
the reasonableness of the application of the facts recorded to the
inference drawn from other sources. The difference only rests on the
question whether vitalized or non-vitalized matter is the _fons et origo
mali_.
How is the production of new matter, resembling that originally causing the
disease, to be explained by any known hypothesis, except on the assumption
of living organized matter? Though Liebig and Mulder both deny the fact,
that the Torula cerevisiae is the sole agent in the process of
fermentation: they both equally fail in shewing upon what it does depend,
and their difficulty rests entirely on their incapacity to explain the
uniform reproductive properties of the matter engaged in this, as well as
in all other allied operations. Liebig's statement {111} however on this
matter requires notice--he says, "that _putrifying_ blood, white of egg,
flesh and cheese, produce the same effects in a solution of sugar, as yeast
or ferment. The explanation is simply this; that ferment or yeast is
nothing but vegetable fibrine, albumen or caseine, in a state of
decomposition."
This state of decomposition, however, involves a much more complex
proceeding, than simply a reduction of matter into its elementary forms of
gases, earths, and minerals; for we nowhere find decomposition of this kind
going on without the development of some organized bodies, either animal or
vegetable: and since we have seen that the spores of the cryptogami are
always in existence in the atmosphere, and making their appearance under
favouring conditions, and especially when we find that fermentation is
invariably accompanied, and I may safely say, preceded by the deposition in
the fluid of the sporules of the Torula, we can hardly believe that they
are any other than the sole agents of the process. I have now a
considerable quantity of the Torula obtained from the urine of a diabetic
patient, in which they appeared, as it were, spontaneously. After the urine
had been allowed access to the air for a certain time, and the whole of the
saccharine matter was converted into new compounds, reproduction of the
Torula ceased;--and those which remained when the process was completed,
still continue as organic cells, deposited {112} in the bottle in an inert
state, but ready, on the addition of fresh sugar, as has been proved, to
resume an active existence. These germs, it is now well known, may be dried
into powder, so as to be blown away like dust without any, or but little,
detriment to their vital energies; and there is now no doubt that they
exist in this condition in the air, as do the spores of mucor, aspergillus,
oidium, agaricus, and all other fungi.
Mulder, however, does allow some properties to the yeast vesicle; he says,
"a variety of strange ideas have been entertained respecting the nature of
yeast; recent experiments have convinced me that it undoubtedly is a
cellular plant consisting of isolated cells. They resemble the composition
of cellulose in some respects, but differ from it in many." "These
vesicles, consisting of a substance resembling that of cells, do not
contribute in the least to the fermentation, but are exosmotically
penetrated during fermentation by the protein compound." These chemists
seem to have an instinctive horror of allowing any active properties to the
yeast vesicle, that is as far as the conversion of sugar into carbonic acid
and alcohol is concerned in the act of fermentation. Dr. Carpenter, as if
desiring to conciliate the chemical and physiological disputants, considers
that the truth is to be found in the mean of the two extremes,--that is,
that the process of fermentation is neither entirely dependent on chemical
laws, nor on those laws which preside {113} over the growth of reproductive
matter, but is a process in which both perform certain offices, each
depending on the other to produce the combined result; he thus approaches
more nearly to the theory of Mulder, than that of Liebig.
But to revert to Mulder, he speaks of the Torula cells being "exosmotically
penetrated during the process of fermentation by the protein compound." Now
the Torula is acknowledged to be one of the Fungals, and the chemical
constituents of the Fungi approach very nearly that of animal tissues. They
contain a peculiar principle, residing in and obtainable from them, termed
Fungin, which is as highly azotised as animal fibre. The protein compound
alluded to, Mulder says, is not gluten, because insoluble in boiling
alcohol, and not albumen, because it is very readily dissolved in acetic
acid, and he regards it as a superoxide of protein. This superoxide of
protein can only have been produced by a vital action in the cells of the
Torula, and as the fungi consume oxygen, and give out carbonic acid, we
clearly have all the elementary conditions for their growth in almost all
decomposing animal and vegetable matters. It is the nature of the fungi to
live on organized matter, but always when it has a tendency to decay; it is
for this reason they have been called "Scavengers." Again, we can
understand why some animalized or nitrogenous matter should be necessary
for fermentation, otherwise fungi could not grow, nitrogen being an
essential constituent of {114} their structure, and further fermentation
does not commence without the presence of oxygen, and like as in animals,
this gas supports their existence. The conversion of sugar into alcohol is
represented by the following formula:--
RESULT.
Sugar. Alcohol. Carbonic Acid.
Hydrogen 3 3
Oxygen 3 1 2
Carbon 3 2 1
If therefore the process were merely of a chemical nature, where is the
necessity for atmospheric oxygen to accomplish the end? it is quite certain
that fermentation cannot go on without its presence. Let us compare the
action of ferment or yeast in a dried state to the action of albumen, which
Liebig says is sufficient when decomposing to set up fermentation. "The
white of eggs when added to saccharine liquors requires a period of three
weeks, with a temperature of 96deg F. before it will excite
fermentation."[42] But any saccharine liquor on exposure to the air, though
entirely destitute of albumen or gluten, will ferment, and the Torula may
be found in it. I have found the Torula in a great variety of syrups which
have spontaneously undergone fermentation. I have also discovered that the
development of the cells is delayed or accelerated by the nature of the
ingredient used in flavouring {115} the syrups, with other peculiarities
which need not here be mentioned.
But the conversion of starch into sugar by means of gluten requires some
notice, as by some persons it is associated in their minds with the organic
process of fermentation.[43] Mulder ascribes the latter in the first
instance to the action of heat, evidently believing that the
pseudo-catalytic operation of gluten upon starch is the type of all such
actions, and regarding them all as simply chemical, but we here distinguish
a wide difference; in the latter instance the gluten is decomposed, and
rendered unfit for a repetition of the chemical phenomenon, and if it is
desired to renew the action fresh gluten must be obtained, and a certain
temperature kept up, otherwise the experiment fails. How different is
fermentation: in the ordinary temperature of the atmosphere the yeast
vesicle will multiply, no incremental or unnatural addition of heat is
requisite, and it is one of the commonest and most natural instances of
vegeto-chemistry: the grape cannot shed its juice, nor the sugar cane its
sap without admitting these germs, which, under certain {116} conditions
multiply themselves and convert the saccharine elements into new compounds.
The method by which the conversion of starch into sugar is accomplished is
thus described by Dr. Ure. He says that if starch one part be boiled with
twelve parts of water and left to itself, water merely being stirred in it
as it evaporates, at the end of a month or two in summer weather it is
changed into sugar and gum, bearing certain proportions to the amount of
starch used. But "if we boil two parts of potato starch into a paste, with
twenty parts of water, mix this paste with one part of the gluten of wheat
flour, and set the mixture for eight hours in a temperature of from 122deg
to 167deg F. the mixture soon loses its pasty character, and becomes by
degrees limpid, transparent, and sweet, passing at the same time first into
gum and then into sugar."--"The residue has lost the faculty of acting upon
fresh portions of starch."
Four points of contrast present themselves for notice as elements of
comparison with true fermentation. 1st. The starch solution has to be
boiled, so that heat, by which it is to be supposed that the starch globule
is ruptured, seems to be an essential portion of the chemical change, and
even this may in fact alone be sufficient in such a case to produce some
elementary change in the starch, and may prepare it for the subsequent
catalytic action of some related organic, though not vital material.[44]
{117} 2nd. Not only a summer heat is necessary, but a period of one or two
months time must elapse before the starch with the water simply becomes
converted into sugar, and if artificial heat is to be used to hasten the
operation, a temperature from 122deg to 167deg F. must be resorted to in
order to obtain the desired result. 3rd. When even this is accomplished
there is no reproduction of the fermenting matter, and artificial and
chemical means must again be applied to repeat the experiment. 4th. The
conversion of starch into sugar can be accomplished without the presence of
gluten at all, by the aid only of temperature and time. It seems to me,
therefore, to be entirely unnecessary to occupy more space in the
elaboration of a proof of the doctrine that the germs of the Torula are the
sole agents in the conversion of saccharine fluids into alcohol and
carbonic acid. By another chemical process starch can be converted into
sugar, but I am not aware that hitherto any method has been discovered by
which sugar can be converted into alcohol except by the process of
fermentation proper.
I have been thus particular in commenting on this subject, as it bears, in
an especial manner, on the question under consideration.
{118}
The physiologist cannot afford to lose this process from the category of
chemico-vital, or biochemical manifestations.[45] The philosophy of the age
has a tendency to make every thing chemical; it is true that the Divinity
is as much seen in the laws which govern the elementary particles of
matter, as in those laws which preside over the transmutation and
sustentation of those elementary and inorganic particles, when compounded
in the tissues which are engaged in the formation of living beings. The
laws by which acids and alkalies neutralize each other, and the affinities
single, double and elective, which the particles of matter exhibit,
together with the influences of light, heat, and electricity upon almost
every condition of matter, are as truly wonderful as the creative power.
Man may, in many instances, imitate the processes of nature, he can render
iron magnetic, and form alkaloids, but the {119} laws which govern the
particles of matter are still the secret of the whole proceedings. We do
but interpret the language of nature in discovery, the book is ever open
before us, and every atom of the world is a word and a theme, capable of
occupying the short span of sublunary existence allotted to man. We have
read of "sermons in stones," but a book has been written on a "pebble."[46]
To return, as we every where in nature find a gradual transition in the
forms, arrangements and properties of matter, so we may expect to find a
link between the inorganic and vital chemistry of nature. The fungi, by
which we contend this transition appears to be accomplished, are also a
link in chemical composition, between the animal and vegetable kingdom, and
not only in that, but in their subsisting upon matter which has been
organized, they are deoxidizers and reducers, as the vegetable kingdom in
its highest function is a compounder. To their functions and offices in the
great scheme of creation, we may fairly apply ourselves with a sure and
certain result of the most interesting discovery. Is it no hint that
wherever decaying organic matter is found, there do we find fungi? is it no
hint that they are found in all parts of the world? that even in snow the
germs of fungi will grow and multiply to such an extent, according to Capt.
Ross, that the protococcus was seen {120} by him, clothing the sides of the
mountains at Baffin's Bay, rising, according to his report, to the height
of several _hundred feet_, and extending to the distance of _eight miles_?
Even stones contain in their interior, or interspaces of their structure,
the germs of fungi. A species of Tufa is found in the vicinity of Naples of
a porous texture, which, when moistened and shaded, produces vast
mushrooms, four or five inches high, and eight or ten inches broad.[47]
This author further says: "In the Maremma, where the volcanic tufa is the
basis of the soil the surface is intermixed with the animal remains of
departed empires, and the ordure of cattle, is covered with grasses of old
pasturages, and is wet with heavy dews. Everything, therefore, conspires
there to a fungiferous end."
They are found growing in and upon both vegetables and animals. Nees von
Esenbeck imagined, that minute forms multiplied themselves in the
atmosphere; and really, when we consider the amount of effluvia composed of
the atoms cast off from the bodies of living or decaying organic matters,
which are incessantly passing into the atmosphere, the conjecture is not an
unreasonable one. The minuteness of those, which we know are always found
growing on decomposing bodies, does not preclude the possibility, nay,
further favours {121} the probability, that others infinitely more
minute,[48] may be destined to remove the more subtle and vaporous
particles which escape into the air.
We can, therefore, I think, conclude, that the lower tribes of vegetation,
may consistently be regarded as capable of existing in almost any
condition, and almost under any circumstances, they may be made to grow in
plants by inoculation, as shewn by De Candolle, and Dr. Hassall. If the
stem of wheat also is inoculated with vibriones, they will make their
appearance in the grain.[49] If the seed contain them and have not lost its
germinating properties, these worms will be found again in the grain. If
the grain containing them be dried for years, and moistened again with
water, these animalcules, according to Bauer and Steinbach, will present
all the phenomena of life. This experiment I have witnessed, and can
confirm the statement. These animalcules in the diseased grain, have under
the microscope the appearance of an immense {122} number of eels crowded
together in a small space, and presenting a movement more, perhaps,
vermicular than any other, and it is continued for a considerable time. Now
if these animalcules, or their ova, can be proved to pass with the sap to
the seed, there can be no difficulty in comprehending how germs,
considerably more minute and of a vegetable nature, should be found subject
to the same peculiar mode of obtaining an entrance into animals and
vegetables for sustenance. "It is usually imagined," says Dr. Carpenter,
"that the germs liberated by one plant are taken up by the roots of others,
and being carried along the current of the sap, are deposited and
developed, where vegetation is most active."
The chemical theory of disease would be better sustained by a comparison of
"the artificial formation of alkaloids," and the phenomena of
transformation of blood into the tissues of animals, and their degeneration
into effete matters, and of sap into the tissues of plants and their
degenerations.
Professor Kopp of Strasburg, says, "In a chemical point of view, the
alkaloids are remarkable for their composition, for their special
properties, both physical and chemical, and for the interesting reactions
to which many of them give rise, when exposed to the influence of different
reagents. Considered medically, the organic bases are distinguished by
their energetic properties. They {123} constitute at the same time, the
most violent and sudden poisons, and the most valuable and heroic
remedies."
Upon this very intricate and interesting part of chemical philosophy, it is
rather dangerous to enter without a thorough and practical knowledge of the
subject. This, however, falls to the lot of few men. We, who are engaged in
the study of disease, and of the best methods of cure, are obliged to take
the investigations of the analytical chemist, and examine them for
ourselves in the intervals of leisure allowed us during the active exercise
of our calling. Though with less advantages for the study of these
transcendental relations of organic and inorganic matter, we are not,
nevertheless, precluded from forming our opinions on their practical
bearings to the phenomena and treatment of disease.
That there is a matter of a poisonous nature concerned in the production of
endemic and epidemic affections, cannot be doubted by any one; I believe
indeed, that the chemical theorists admit this, at all events Liebig does,
for he says, "The morbid poison changes in the blood are fermentative, just
such as occur in beer making." If we start, then, with the consideration
that poisons, in a chemical point of view, are the objects of our research;
the obvious course to take is to enquire what is the source of poisons
generally, and what their effects on the animal economy? The mineral
poisons are entirely excluded from the enquiry by their {124} inaptitude
for diffusion, and their uniform effects upon all persons, differing only
in degree in their operation. The same objections apply to gaseous poisons,
except that to them the property of diffusion would be admitted.[50] We
come then to the alkaloids, which constitute, as Kopp says, the most
violent and sudden poisons. For the production of alkaloids by artificial
means, organic products of some kind are required. Artificial heat,
powerful chemical agents or length of time, are, as far as information at
present extends, the indispensable requirements to induce these peculiar
changes in matter. The only instance I can find, in which elementary
matters can by artificial means be combined, so as to resemble the products
of nature, is that of the conversion of carbon and nitrogen into cyanogen.
But the process by which this is accomplished, leads rather to doubt
whether it be really and simply by a combination of _elementary_ carbon and
nitrogen. I extract the following from the Annual Report of the Progress of
Chemistry, for 1848. "H. Delbruck has performed some experiments on the
important subject of the formation of cyanogen. He confirms the statements
of Desfosses and Fownes, inasmuch as a _weak but distinct_ formation of
cyanogen was observed on igniting {125} _sugar-charcoal_[51] with carbonate
of potassa in an atmosphere of nitrogen." The use of sugar-charcoal, may be
perhaps an explanation of the weak formation of cyanogen, for in these
numerous and successive chemical changes of matter, it is impossible to say
how many sources of error may arise. The constant contradictions of each
other, and the opposite statements made by chemists, of equal eminence,
leave us in a wilderness of doubt, from which we are not likely to be
freed, until definite laws shall be discovered to act as a guide in the
comprehension of the higher branches of Chemical Philosophy.
But supposing that the generation of alkaloids could take place in the
body, or some analogous poisonous matter, we have yet to imagine a whole
host of peculiar and essential conditions to effect this change, besides an
atmospheric agent or agents to set in motion those compositions and
decompositions, capable of bringing out these new products from the
elements of blood. We are aware that in the blood, carbon and nitrogen are
sufficiently abundant as well as saline compounds, to generate cyanides,
and, with hydrogen also there in plenty, hydrocyanates, and thus from them
many other poisonous products, but how is all this to be effected? And even
if effected, it is yet a question if such compounds can in any way simulate
the attacks of epidemic disease. We have {126} already shewn that the
amount of most poisons necessary to destroy an individual, can be pretty
clearly estimated, and their _modus operandi_ is tolerably well understood.
Again, the most essential part, in which all chemical theory fails, is an
explanation of the reproduction of contagious matter.
The catalytic process, by which decompositions are said to be effected, and
in which Liebig includes the various fermentations, is one of those
chemical relations of matter to matter, considered by some as the probable
cause of infection. Mr. Simon, in a late lecture, has said, "I consider the
phenomena of infective diseases, to be essentially chemical, and I look to
chemistry to enlighten the darkness of their pathology. Qualitative
modifications, affecting the molecules of matter as to their modes of
action and reaction, are such as form the subject of chemical science; and
those humoral changes which arise as the result of infection clearly fall
within the terms of its definitions." Further on he adds: "The phenomena of
infected diseases appears then, in many respects, to be sui generis.
Certainly they are chemical. _Probably_ they belong to that _class_ of
chemical actions called _catalytic_."[52]
{127}
It is not improbable that something resembling a catalytic action may take
place in the blood in those diseases of endemic and epidemic origin, but
that it can be by a chemical process alone is contrary to all experience of
catalytic operations, for except in the instance of fermentation proper,
there is no multiplication of the fermentative matter. The action of the
matter of contagion seems to stand on the confines between electro-chemical
and bio-chemical manifestations, and so long as no chemical explanation can
be given for the multiplication of the matter of infection, the most
rational course to adopt is to assume that life under some unknown form is,
as we every where find it, the sole reproductive agent.
* * * * *
{128}
SECTION II.
THE ANIMALCULAR THEORY OF EPIDEMICS UNTENABLE.
The animalcular theory of disease, after remaining almost unnoticed for
nearly two centuries, has been again revived under the auspices of Dr.
Holland in this country, and Henle of Berlin. And though not entirely
buried in obscurity, this theory had completely failed to modify the
practice of physicians in the treatment of those diseases which were
supposed to owe their existence to these invisible atoms of created being.
The resuscitated notions and all their amplifications, to which the advance
of science has contributed so much, are threatened with a like fate, an
absence of all practical results.
Though I would not attempt to deny the possibility, nay, even the
probability, that insect life may yet be discovered as the cause of some
diseases,[53] still {129} there are many and cogent reasons against both,
and which are at variance with facts and observations. Where insect life
has been found associated with disease, it more especially appears as a
consequence than as a cause.
Disease, in its most enlarged sense, is a conversion of one form of matter
into another; it is a transformation of healthy blood and tissue into new
and abnormal products. Where insects in all their variety of forms are
discovered, their voracious propensities are their chief characteristics,
they are the consumers of matter after its partial disintegration, if
animal matter be their food, unless they be carnivorous and predacious, or
if herbivorous they usually feed upon the tender shoots of plants. Thus far
we are certain of the manner in which insects destroy living matter; it is
a process the unassisted eye may every where witness, and which experience
has amply attested. To take, however, the animalcular world as it presents
itself to us under the microscope, and as the intermediate step between the
manifest and the hidden for a fairer and more direct method of reaching the
truth, what do we observe to be the ruling law of infusory instinct? They
live to feed; the term polygastrica sufficiently implies their natural
tendency to consume. The simplest form of animalcular life, seen in the
genera of monads, still preserves the animal character by possessing a
stomach or stomachs in which the food is received, to be digested for the
nourishment of the {130} system; and even some of these minute objects
which vary in size from one _two-thousandth_, to one _three-thousandth_ of
a line in diameter, are said to be carnivorous and predacious. Upon this
fact alone, I would place the improbability of insects being the cause of
epidemic disease. Each insect doubtless has its own peculiar food, and
whether it be a vegetable or animal feeder, it consumes the matter already
organized for conversion into its own tissue, and the only change which
could be affected by them in the blood, would necessarily be that of
appropriation of some one of the constituents as an element of food; when
that food is digested, (taking digestion generally as an identical
process,) the excrementitious matter is composed of secretions and
disorganized matter, mixed together as an _effete_ product, and destined
then for reorganization by the vegetable kingdom. Now all animals, whether
they be large or small, live on organized matter,--they convert that matter
into an inorganic form, and I cannot help imagining that if epidemic
diseases and fevers depended upon animalcular growth and development in the
blood or tissues of the body, the excretions or secretions from them would
have yielded some information to the searching enquiries of the chemist,
supposing that these excretions and secretions were capable of reaching to
a sufficient amount in quantity, to bring about those fatal effects of
poisoning, we witness in Cholera and other epidemic affections. Insects, I
{131} believe are poisonous only by their secretions, and though they are
known to multiply with exceeding rapidity, I can hardly imagine that by
their development, however rapid, they could produce such a change in the
human body, as to bring about the speedy dissolution, and generally
gangrenous appearance, that has invariably been observed in those suddenly
dying under the influence of epidemic poisons. The vibriones, whose
destructive effects on wheat are so well known, are a genus of animalcules,
which at first would seem to favour the animalcular theory in a remarkable
manner; for on examining them, they do not appear to possess any other
structure than a gelatinous absorbing mass, in this respect resembling a
vegetable.
But Ehrenberg's scrutiny corrected the error of De Blanville, and shewed,
that they were far from being agastria, or stomachless animals. The Rev.
William Kirby says, "Ehrenberg has studied the vibriones in almost every
climate, and has discovered, by keeping them in coloured waters, that they
are not the simple animals that Lamarck and others supposed, and that
almost all have a mouth and digestive organs, and that numbers of them have
many stomachs." All the discoveries indeed which have been made on the
minuter forms of animal life, have tended to confirm the doctrine that the
stomach is the exponent organ of an animal; that is, in all animals there
exists, in a variety of modified conditions, a receptacle for food. Some of
the {132} animalcules, however, are still supposed to exist by absorption,
as the vinegar eel, _vibrio anguilla_,[54] but when we find that the law
is, generally speaking, that the receptacles of food become multiplied in
number in these minute beings, and the vibriones which were supposed to be
stomachless, have been proved to emulate their associates in the number of
these organs; it would be more reasonable to conclude that our imperfect
vision is the barrier to their detection, rather than to suppose that they
do not exist. Besides, when we are told on undoubted authority that some of
the animals of this class, have as many as _forty or fifty_ stomachs; the
least we can do, is to allow that all of them possess, at least one
digestive organ, though we may not be able to detect it.[55]
So far then for the consideration of animalcular structure: let us now more
particularly enquire into their destructive habits, and their functions,
inasmuch {133} as they may be supposed capable of engendering epidemic
diseases and fever. The truly carnivorous animalcules, or those truly
herbivorous in their instincts, we may presume to be beyond the limits of
our enquiry. We have rather to do with those which take an intermediate
position, namely, those which feed upon matter undergoing decomposition, or
upon fluids containing organic matters in solution, or suspension. If we
take Entozoa generally, they may be considered as most conveniently to be
placed in this intermediate class; and here we find still the digestive
apparatus, and more than this,--for upon the modifications of the organs
appropriated to digestion is their classification founded. "Rudolphi
divided the Entozoa into Sterelmintha, or those in which the nutrient tubes
without anal outlet are simply excavated in the general parenchyma, and
into the Coelelmintha, in which an intestinal canal with proper parietes
floats in a distinct abdominal cavity, and has a separate outlet for the
excrements."[56]
How do these animals obtain their sustenance, and what changes can they
produce upon the vital fluid of the body? Analogy is here our only guide.
If the trichina spiralis is examined, it is found to be enclosed in a cyst
containing fluid; and this is, {134} doubtless, the source of its
nutriment, and contains in solution the elements for its nutrition; but in
this instance there is no selection, and there can be no locomotion to an
extent sufficient to imply searching for food, as the animalcule in its
natural state, when taken from the human muscle, is found coiled upon
itself, making about two and a half turns. The fluid of the cyst is thus in
all likelihood prepared by endosmosis, for the immediate and appropriate
nutrition of the parasite. The cyst is thus the part which performs the
diseased process, the containing animalcule is merely the consumer of what
is prepared for it by the cyst. And this would seem to be the rule with all
parasites, of the encysted kind.
We have alluded to the vibriones which are found in the fluids of living
bodies, and the trichina which is found in the solid muscle; we have now to
refer to those which infest the cavities. It was, I believe, Ehrenberg, who
shewed that the tartar which accumulates on the teeth is composed of the
debris of minute animalcules; in fact, that it consists of calcareous
matter, having once formed a portion of the structure of their bodies, the
ubiquity of these creatures is therefore as much and clearly established as
the lower forms of vegetation. The intestinal worms, of which perhaps the
Taenia is the most curious and important to be noticed, are from the
locality in which they are found, chiefly injurious by the irritation they
set up, and by appropriating {135} to themselves the nutrient juices
elaborated in the process of animal digestion, thus depriving the
individuals they infest of that which was destined for their own
nourishment. In this, as in all associated instances, the character by
which these parasitic animals are marked is their consuming propensity.
There is, however, one more observation to make upon parasitic growths; but
the question is yet unsettled in what kingdom of nature is the
acephalocyst, or hydatid, to be placed. Mr. Owen says, "As the best
observers agree in stating, that the acephalocyst is impassive under the
application of stimuli of any kind, and manifests no contractile power,
either partial or general, save such as results from elasticity, in short,
neither feels nor moves, it cannot, as the animal kingdom is at present
characterized, be referred to that division of organic nature."
We thus arrive at the simple cell, and the multiplication of living beings
by cell buds; it is the point at which the confines of the animal kingdom
are reached, and at which we are driven to speculation. The hydatid lives
like a plant, by imbibition; and procreates, like a plant, by budding,
either endogenously or exogenously, as regards the original or parent
cell.[57]
{136}
This condition of being, suggested the notion of Protozoa, or first
animals, in the same way that the purely cellular plants, that is, each
individual, consisting of a single cell, gave the idea of Protophyta, or
first plants. Mr. Kirby thus expresses himself on this subject: "The first
plants, and the first animals, are scarcely more than animated molecules,
and appear analogues of each other; and those above them in each kingdom
represent jointed fibrils."
Admitting, then, that animals as well as plants exist in the form of simple
cells, and that their multiplication proceeds apparently upon the same
principle in each, it is nevertheless abundantly manifest, that the
cellular form of perfect individuals is infinitely more numerous in the
vegetable than in the animal kingdom.
{137}
From the mosses downwards to the fungi, the whole structure of the plants
consists of an aggregation of cells, more or less in number and complicate
arrangement, until, through a variety of gradations, we reach the single
cell as a perfect individual.
It is rather remarkable, that the lower forms of vegetables and animals
seem to derive their nutriment from matter of a similar kind; and though
the office of plants is as a rule, to convert inorganic into organized
matter, it appears that some of the fungi may live as animals do on organic
matter when in a state of solution. This, however, is uncertain; for we do
not know what are the first signs of decomposition in organized bodies, and
for aught we can tell, it may be perpetually going on; so far as the
disengagement of carbon from the system is concerned, this is certain; but
whether the nitrogenous compounds also are subject to a resolution into
their elements in the living body, is another question, and not so easy of
solution. The partially decomposed elements of animal structures are,
however, particularly adapted for the nutrition of the lower forms of
vegetation; it is, indeed, from the decaying organic matters that the fungi
derive, it may be said, their entire food.
* * * * *
{138}
SECTION III.
SKETCH OF THE PHYSIOLOGY AND PATHOLOGY OF PLANTS AND ANIMALS.
Animals and plants depend for their existence upon a nutritive fluid, which
permeates their structure; it is the element from which all their
secretions are formed, and their organs are nourished.
The food of animals is composed of previously organized matters, and is
conveyed into a reservoir called a stomach, where it undergoes a process of
solution, previously to entering the circulation. At this period, the
animal and the plant again present points of resemblance, the lymphatics or
absorbent vessels take up the products of digestion, and convey them to the
blood-vessels, where mingling with the current of the blood, they are
conveyed to the lungs, there to undergo a process of oxygenation before
they become fitted for the renovation of the tissues of the body. Such is
the nature of the food of man, that it contains all the elements necessary
and adapted for transformation into bone, muscle, brain, and parenchyma, as
well as the other tissues of the body; besides other elementary matters,
which, though they form a very insignificant portion of {139} animal
textures, from their constant presence in the vital fluid, evidently
perform some important offices in the general economy of life; they are
partly, perhaps, occupied in forming constituents of secretions.
Plants do not require a stomach,--the humus or soil to which they are fixed
is the laboratory, where the nutritive matter is prepared in a state fit
for absorption by the spongioles of their roots, and these correspond to
the lymphatics of animals; after being taken up by the spongioles, this new
fluid mingles with the sap, and passes to the leaves or breathing apparatus
of plants, where carbonic acid gas combines with the crude vital liquid,
and converts it into a condition fit for all the offices to be performed by
the plant: viz. the growth of tissues, and the elaboration of secretions.
The tissues, however, of plants, though more simple in their nature,
present a much more varied character than those of animals, when the
different species are compared.
The bones of animals which give them their form, are invariably constituted
of phosphate and carbonate of lime, deposited in a matrix of gluten;
muscle, nerve, brain, tendons, and ligaments, have nearly, if not
completely, an identical composition throughout the whole range of the
animal kingdom: their secretions, however, vary much more considerably, as
also do the secretions of vegetables. But vegetable tissue may contain, as
in the stems of {140} grasses, a considerable amount of silex, and some
notable quantity of sulphur, and so essential to their existence is the
former element, that they cannot live without its presence in the soil, and
also with it an alkali, to render it soluble. A large amount of soda, is an
invariable attendant upon the structure of marine plants, as potash is of
those growing on the land.
Thus, whether we regard the health of animals, or vegetables, we discover,
that besides the matters which are absolutely indispensable for the
nutriment of the tissues which undergo rapid transformation, those of a
more permanent and durable nature require in an almost insensible degree, a
restitution of elements; and though not apparently absolutely necessary to
preserve vitality in the being, yet have so marked an influence over it, as
to indicate an extensive bearing of each individual part, on the whole
associated entity.
The elementary tissues of both kingdoms have been traced, in whatever form
they may be found, to a cellular origin. The minutest vegetable germ, is a
cell containing a granular matter within it, and even man himself, in his
embryonic state, may be represented as an insignificant point in the realms
of space; and might be placed side by side with the smallest particle of
living matter, without suffering by the comparison.
The laws by which the development of these elementary cells is regulated,
so that each advances {141} to its limit, and fulfils its destination, is
one of those inscrutable and overwhelming mysteries of nature, which leads
the admirer of creation on and on into the abyss of the future, and fills
his soul with aspirations for that time, when the veil of ignorance shall
be withdrawn. But this is not my subject.
The organization of the two animated kingdoms, is then regulated by
definite laws, and all matter, whether acting upon them as agents of
nutrition or destruction, are equally under their dominion; to investigate
and to endeavour to fathom some of these laws, is the aim I have in view.
The sap is to the plant, what the blood is to the animal,--the elements of
nutrition and secretion are contained in it, and whatever interferes with
its normal constitution by subtracting from, or adding to it, deteriorates
its qualities, and retards or accelerates the functions of the individual.
Excess or deficiency of the natural elements may also be a source of
disturbance; if carbonic acid be too abundantly liberated in the soil, as
Dr. Lindley expresses it, "plants become gorged;" and if, on the other
hand, the elimination be too slow, they become starved. It has been also
shewn, that plants though they give out oxygen from their leaves, do not
throw it off as animals do carbonic acid from their lungs; but that this
arises as a result of digestion, and the fixation of carbon in the system,
and that they really respire oxygen as {142} animals do, and give off
carbonic acid, both by day and night.
That light is the stimulant of the digestive functions, and that,
therefore, during the day, the amount of oxygen thrown off, far exceeds the
amount of carbonic acid liberated during the same period.
The great and important distinction between animals and plants is, that the
former possess a nervous system, by which they are subject to a very
extended series of psychological relations; it is in these chiefly, if not
entirely, that we are to look for the distinctive and well-marked
differences of diseased action. In animals there are special media of
communication between the sources of dynamic power, and the parts upon
which the force is exercised: and again, a return communication exists,
which conveys impressions to the source of power, and to use a simple
comparison, a system of telegraphing is in incessant and watchful
operation. This force is influenced and modified in its action, when
exercised in the regulation of nutrition, growth, and reproduction of
tissues, by the passions and emotions of the mind. All the secretions and
functions of the body are more or less susceptible of being accelerated,
retarded or modified by the psychical relations of mind and matter. Though
we are apt to imagine that in man alone, these phenomena obtain much
importance--there can be but little doubt, that wherever a {143} nervous
system exists, whether in the form of aggregated or diffused ganglia, the
interdependence of force and organization, each upon the other, bears a
certain and definite physiological comparison; the more aggregated the
ganglia, the more close, intimate, and extensive the psychical connexions,
and the gradations pass downwards, until they appear to be lost on the
confines of the vegetable kingdom.
The diseases of plants and animals deserve a more careful comparison than,
I think, has hitherto been bestowed upon them.[58] If the study of
physiology, or an enquiry into the laws which regulate the functions of
living beings in a state of health, has been materially aided by the
intimate knowledge of vegetable physiology, which, from the simple
structure of plants, so favours the experiments of the student, there is
every reason to suppose that vegetable pathology may also lead us to an
equally important and useful result.
It is quite certain, that if a healthy seed, or leaf-bud, be placed in such
a situation, that, according to the laws known, it will in all likelihood
germinate, if all the elements for its sustenance exist in the soil, and
the temperature and hygrometric {144} condition of the atmosphere are
adapted to it, a healthy plant will be the result. Light, heat, moisture,
and soil are therefore to be considered as the agents required to exist in
a certain balance, or proportion, in reference to the health or power of
vitality of the plant. Within a certain amount of variation, health may
persist in virtue of the power of selection, which appertains to the
spongioles of the root in absorbing nutriment; and also as regards light,
from the tendency which most plants have to accommodate themselves to any
deficiency of this element, by presenting their leafy expansion in that
direction where the most of its influence may be obtained. But beyond a
certain limit an unhealthy condition sets in. If the soil contain not the
inorganic elements, which are absolutely indispensable for the tissues of
the plant, or even if they be there and not in a state to be absorbed, a
dwindling and degeneration ensue; if light be deficient in quantity,
pallor, feebleness, and elongation of tissue follow, with more fluidity and
general softness of texture. These conditions of plants have their
analogues in the ill-fed and ill-nourished children in some of our
manufacturing districts; they are stunted and diseased. Transport a healthy
country lad, with the bloom of health on his cheek, from his native hills
and valleys, or woods and fields, to the stool behind a desk for eight
hours a day, in a narrow street in any city, where the rays of the sun
rarely penetrate, it will not be long before {145} the skin of the animal
and the cuticle of the plant may be submitted for comparison, when both
will testify to the importance of the solar rays, as an indispensable agent
in supporting the normal processes of organic life. So far common
observation is competent to a solution of the facts; but beyond this we
come to the enquiry, what resemblances are there in the early conditions of
plants and animals. Each originates from nucleated cells, endowed by the
All-seeing Power with a blind impulse of progressive development; the most
simple cell of a vegetable multiplies itself by a generation of new cells
within it, when the parent dies, and liberates the offspring. Here
progression is simply multiplication; it is, as it were, progression in
length only. The original cell, however, of animals, which is styled the
germinal vesicle, extends or becomes developed into dissimilar parts; and
whatever may be the variety, all alike proceed from the original germ cell,
and the _tout ensemble_ of parts constitutes the one and indivisible whole;
in this instance there is addition besides multiplication, tissues and
organs are added in all variety, until the maximum of organic development
is attained in the wonderful being, man.
Yet how many points of resemblance are there between the vegetable cell and
the fully developed human being, in a physiological and pathological point
of view. There must be nourishment to sustain both; both require a certain
amount of light {146} and heat for their growth and increase, and are
dependent upon various unknown causes for active and healthy existence; and
when a certain time has expired, all alike return to a condition, in which
the particles composing them are subject only to the dominion of the laws
which preside over inorganic matter.
But during the existence of plants and animals, we discover other features
of comparison; plants, as well as animals, are liable to disease; they are
subject to functional and organic affections. The former, among plants, are
usually traceable to atmospheric vicissitudes or irregularities, changes of
situation, &c.; and in man to irregularities of diet, and mental and bodily
excesses, as well as to atmospheric vicissitudes.[59]
The organic diseases of plants and animals depend upon a repetition, or
continuance, of functional derangement. As a consequence of this, the
nutrition and reproduction of tissues lose their normal and definite
character, wherefrom an indefinite and abnormal result is obtained. There
is a limit to abnormal productions, and they are apparently {147} subject
to laws, though not yet understood. In animals, they may be either
excessive development of natural tissue in natural localities, as obesity
and fatty tumours; they may be natural products in unnatural situations, as
fatty degenerations of muscular tissue; or altogether new and unnatural
products, as tubercle and cancer.
In plants, from their greater simplicity of structure, organic affections
are perhaps entirely limited to the two first forms of animal organic
disease; viz. to undue development of tissue in natural situations, and to
the formation of natural tissue in parts of a plant where they are not
usually found in a state of nature. The variety of excrescences seen on the
stems, branches, and twigs of plants, may be given as instances of the
former; and the conversion of stamina into petals, as in double flowers, as
an instance of the latter.
We derive our sustenance from vegetables, and they from us; they produce
for us the soothing opiate and the deadly strychnia; we for them the
animating ammonia, and the distortions and sterility of excessive culture;
we engender in them, by the latter, debility, disease, and death; and in
our turn we become their prey. All this indeed is but a cycle of events,
that requires no learned mind to fathom, and to comprehend; it is a matter
of every day occurrence, and, though perhaps not entirely unheeded, is not
dwelt upon in the fulness of its bearings and importance. {148}
Let us now consider the diseases of plants, as a study progressive to those
of man; and as their physiology has so extensively served us, we may
possibly also find in their pathology much material for instruction; not
that it will be attempted to shew that the same diseases affect both
kingdoms, but that diseases, though dissimilar in effects, may have similar
sources.
Unfortunately, there are not many men in this country, who need go further
than their own gardens to find abundance of disease among their fruit trees
and vegetables. The vine, the apple and the potato, common to most gardens,
will furnish specimens.
It is an error of a serious kind to suppose, that the parasites which
infest plants are not essentially the cause, or, perhaps, more properly
speaking, the elements of disease. I confine myself here to disease of
parasitic origin, as that is the subject of which I am chiefly treating.
That parasitic growths are the elements of disease in some instances, is
now beyond dispute. The experiments of Mr. Hassall, detailed in Part II. of
the Transactions of the Microscopical Society of London, are most
conclusive; and they are of that simple nature, that any one may convince
himself of their accuracy, by a repetition of them from the directions
there laid down.
He says, the decay is communicable at will "to any fruits of the apple and
peach kind, no matter {149} how strong their vital energies may be, by the
simple act of inoculation of the sound fruit with a portion of decayed
matter, containing filaments of the fungi. We may use with success the
sporules of such fungi; but in this case the decomposition does not set in
so quickly; in the one case, the smaller filaments of the fungi have
advanced several stages in their growth; while in the other, the sporules
have yet to pass through the several stages of their development."
Mr. Hassan, however, seems to speak doubtfully as to the mode in which the
disease becomes naturally introduced;[60] how the spores enter the fruit,
"is not very clear--though probably, it is by insinuating themselves
between the cells of which the cuticle is composed, or perhaps by means of
the stomata, where they are present. I may here state that the experiments
were made on fruit, while living, and attached to the tree."
But why should there be a doubt as to the parts by which the sporules of
minute fungi enter the plant, when it is clear, that not only can they
enter {150} by the spongioles, but by the stomata of the leaves, and mingle
with the sap. It is true, that they make their appearance and grow upon the
leaves and the fruit; but these are the situations most adapted for their
fructification. I have seen the spores of the fungi which attack the
cucumber and vegetable-marrow, in the cells of the hairs, and even their
filamentous prolongations; these appropriate the fluids conveyed to the
cells of the hair, rupture them, and at length fructify.
On referring to Dr. Lindley's Medical and Economic Botany, I find that many
fungi are the active elements of disease, and in a manner which renders it
highly improbable that they are so in any other way, than by obtaining an
entrance to the sap of the plants. Of the microscopic fungus which destroys
wheat, the Uredo caries of De Candolle, we find the habitat to be within
the ovary of the corn, and that 4,000,000 may be contained in a grain of
wheat,--now this and another fungus, the Lanosa nivalis, are said to
destroy whole crops of corn: we cannot imagine that such an extensive
affection, can have any other source than by means of the spores through
the sap, seeing that bruising of the surface, or rupture of the cuticle of
the apple, a comparatively soft fruit is necessary to produce the disease
artificially in them; besides, a grain of corn containing vibriones, when
grown and having fruited, the new fruit also contains them--now here, as
this is I believe almost invariably the {151} case, either they or their
ova must be carried with the sap to the new germs.
It is rather a remarkable fact, that these entophytes appropriate the
nutriment destined for the plant in which they grow, they are consequently
the means in many instances of its entire destruction, though only
partially so in others.
There are many Fungi which have this tendency. The Puccinia gramienis,
"preys upon the juices of plants, and prevents the grain from swelling."
The Aecidium urticae, common on nettles, deprives the plant on which it
grows, of the organizable matter, intended for its own nutrition. The
Erysiphe communis, overruns and destroys peas. The Botrytis infestans,
"attacks the leaves and stems of potatoes." The Oidium abortifaciens,
attacks the ovaries of grasses--and the Oidium Tuckeri, "a formidable
parasite, destroys the functions of the skin, of the parts it attacks." The
latter has been most injurious to the vines, during the last two years. I
have known instances in which the vines have been cut down, and every means
taken to rid the houses of the disease; but this year, it has made its
appearance, with all its former virulence, in the new shoots.
This, however, is sufficient to shew that plants are liable to disease,
depending upon parasitic growths, which affect their vital powers, and
deprive them of their natural nutritive fluids.
But somewhat similar diseases belong also to {152} warm climates; in a
letter from Cuba, dated Dec. 1843,--Mr. Bastian writes, "_a plague_ has
appeared among the orange trees--a mildew attacking the leaves and the
blossoms, which finally dry up. It most frequently kills the trees. None of
the orange family are exempt; lemons, limes, and their varieties, with the
shaddock and forbidden fruit, have all suffered." This disease has
continued without intermission, till the present year,--when the same
gentleman writes, Feb. 20th, 1850: "The evil exists, although in a
diminished degree, so much so, as to have allowed the trees to produce me
30,000 oranges again. In old times, the same plantations produced me
100,000."
The West India sugar-canes are also liable to a disease, which the Rev. Mr.
Griffiths, in his Natural History of the Island of Barbadoes, speaks of, in
the following manner: "This, among diseases peculiar to canes, as among
those which happen to men, too justly claims the horrible precedence." This
disease is called the Yellow Blast. It is difficult to distinguish the
Blast in its infancy, from the effect of dry weather.
There are often seen on such sickly canes, many small protuberant knobs, of
a soft downy substance. It is likewise observable, that such blades will be
full of brownish decaying spots. The disease is very destructive to the
canes. It is observed, that the Blast usually appears successively in the
same fields, and often in the very same spot of land. {153}
This Blast is often found far from "infected places," and the infection
always spreads faster to the leeward, or with the wind.
"_It is remarkable if canes_ have been once infected with the Blast,
although they afterwards to all appearance, seem to recover; yet the juice
of such canes will neither afford so much sugar, nor so good of its kind,
as if obtained from canes which were never infected."
I may here allude to the circumstance, that in the island of Cuba, the
destructive mildew is commonly called, _la pesta_.
It were needless to multiply instances of other endemic and epidemic
diseases of vegetables; they are well known by practical observers to be
very numerous, and I believe, in most instances, depending upon fungoid
growths. The destruction of vegetables by insects, is of a very different
nature to that produced by the fungi; it would be as unreasonable to
consider the consumption of corn and herbage by locusts, as a disease of
vegetation, as the massacre and devouring of human beings by cannibals, a
disease of the human body.
It is true that insects are exceedingly destructive to plants, but as far
as I am able to obtain information, they appear to be so chiefly by their
voracious propensities; they consume the structure of the plant in its
entity, and do not primarily interfere with its vitality. The instance of
the vibriones, before-mentioned, seems at first to be an exception {154} to
the rule, but this is rather apparent, than real; and it may be made to
apply more as a confirmation, than an obstacle to the vegetable theory: for
if we may fairly compare the diseases of animals with those of plants, the
existence of entozoa in the latter, would be considered an essential point
to be substantiated.
Having now considered the question as to the infeasibility of supposing
that chemical fermentation is the basis upon which a theory of diseases can
be sustained, and having shewn that life is inseparable from infection, and
miasmatic generation;--having explained the phenomena of the dispersion of
diseases by comparison with the dispersion of plants, and finally, having
demonstrated that the physiology and pathology of plants bear so close a
relation to each other, and that their epidemic affections depend upon
minute organic germs, I submit to the judgment of my readers, whether there
is not much reasonableness in the application of the facts to the
inference--that living germs are the cause of epidemic disease in man and
animals.
* * * * *
{155}
CHAPTER IV.
RESULTS IN PROOF OF THE TENABLENESS OF THE PROPOSITION.
--------
SECTION I.
OBSERVATIONS ON SOME OF THE LAWS OF EPIDEMIC DISEASES.
The results obtained by comparing certain facts connected with Epidemic
Affections of animals, with analogous affections in plants, afford, from
the few instances I shall here notice, a very strong presumption, that
analogous causes operate in the production of these affections. I have
already quoted from Hecker, to shew that previously to, and during the
Epidemics of the Middle Ages, the minuter forms of animal and vegetable
life appeared to be called into existence, much more abundantly than usual;
that famines prevailed in consequence of failure of cereal crops, no doubt
depending then, as now, upon the various forms of fungiferous growth. I
cannot refrain quoting here, a passage or two from our old friend Virgil;
for he confirms not only the fact of peculiar showers in {156} connexion
with diseases, but he also refers to the rust of corn, thus:
150. "Mox et frumentis labor additus; ut mala culmos
Esset rubigo ...
... Intereunt segetes."
_Georg. 1._
Then:
311. "Quid tempestates autumni et sidera dicam?
. . . . . .
322. "Saepe etiam[61] immensum coelo venit agmen aquarum
Et foedam glomerant tempestatem imbribus atris
Collectae ex alto nubes."
_Georg. 1._
The occurrence of black showers in this country has been observed during
the present year, and I understand that in the fenny countries of the East,
the corn has suffered much from the Uredo. I am not mentioning the
circumstances as cause and effect, but merely to call attention to the
fact, that unusual phenomena of this kind have been generally associated
with disease of the animal and vegetable tribes.
The same causes also predispose plants as well as animals, to epidemic
attacks of disease. The repeated observations in the public journals on the
subject of ventilation, drainage, and over-crowding, render all notice from
me needless, to shew that these, though they do not produce the diseases
{157} treated of, yet that under the influence of bad air, bad drainage,
and over-crowding, epidemics are fostered and spread.
Lastly, says the Count Philippo R['e], "I would remark that if _bad
cultivation, and especially bad drainage, does not produce bunt or smut, it
is certain that those fields, the worst treated in these respects, suffer
the most from these diseases_."
It has been remarked by many observers, that a greater fecundity has
attended upon Pestilences, and this has been proved by comparison, that the
births in proportion have far exceeded the ordinary limit.[62] In
juxtaposition with this observation, I will place the following, not as a
proof, but as a remark made quite independently of the subject of which I
am treating. "From the first the diseased ears are larger than the healthy
ones, and are sooner matured. What appears singular, but which I have not,
perhaps, sufficiently verified, is _that the seeds are more abundant than
in a sound ear_."
{158}
Now these are facts which require amplification, and if these two alone
should be shewn upon an extensive field of observation, to apply not only
to corn, but to other members of the vegetable kingdom, as I doubt not will
be the case, though I am not fully prepared to prove it, it would be
difficult to dissociate the fertility of the two living kingdoms from the
operations of one and the same, or an analogous law.