THE LIVING WORLD--ITS EXTENT AS REVEALED BY THE MICROSCOPE--HOW ITS
REMAINS ARE DISPOSED OF WHEN LIFE HAS CEASED.
§ 1. It has been often remarked, and with great truth, that the world
abounds with life. In the remains of that which had once lived, which
was at one period organic, the illustrious Cuvier and the great
school to which he belonged saw the materials of life, the food, in
fact, of that which exists; he held that between the inorganic and
organic worlds there was an impassable gulf, or in other words, an
inconvertibility or a metamorphosis, call it by what name you will.
This plausible theory, with many others, is now controverted by modern
chemists, who boldly assert that no organic atoms or molecules, as
such, can serve as food for a plant or an animal. But be this as it
may--for chemists admit that the incombustible constituents or the
salts of the blood, so essential to the nourishment or support of
animal life, must have passed through organic bodies[27]--one thing is
certain, that the extent of life on the globe can scarcely be imagined.
For first, as regards the vegetable kingdom, do we not observe how, as
spring and summer advance, the organic beings which during winter had
lain dormant at the bottom, or deeply entombed in the waters (I speak
not of those to be seen at all times on the surface of the earth),
rise to the surface, bringing with them countless myriads of the ova
of aquatic animals and of those which haunt the surface of the water?
Amongst these stand pre-eminent the infusoria or zoophytes; with these
the atmosphere also becomes loaded. They form, in fact, the substratum
of all animal life, constituting the food not only of animals somewhat
larger than themselves, but of many much larger, as the various species
of the cyprinus. Many valuable gregarious fishes, as the herring,
char, and the finer species of trout, live on entomostraca; they in
their turn become the food of larger and more voracious fishes. Even
the whale lives on food a portion of which is almost microscopic. Now,
withdraw the water by which all this life subsists, and putrescence, or
fermentation and decay, must be the result upon a mass of life of which
the amount may be faintly conjectured by the fact that 4,100,000,000
millions of infusoria may be found in a square inch. These insects,
when dead, are found in strata extending to some acres, and many of
the fossils thus discovered belong to species of genera now alive.
The principles of life were at least as active in what we call the
old world (though in reality the young world), as in the present; the
researches of Ehrenberg, repeated by many others, have placed these
opinions beyond dispute.
[27] Liebig.
Now, it is by no means improbable--nay, it is almost certain--that many
species of these infusoria reside in the vapour of the atmosphere.
The Austrian physicians came to the conclusion that the Asiatic cholera
was of local or terrestrial origin; the facts mentioned above confirm
this view to a certain extent, by disproving the general epidemic laws
supposed to regulate the progress of cholera and of fever (in which
cholera usually terminates), and by showing that the disease sought
out, as it were, the inhabitants of certain districts favourable
for the production of the deleterious influences I am now about to
consider. When the epidemical influence was superadded to these, the
disease appeared; its independence of changes in temperature may have
been owing to other circumstances not yet investigated. Connected
with this evolution of vegetable life in spring and summer, and with
its effects on man, is what is called the blooming of plants. The
presence of stagnant waters and of foul ditches may be discovered even
at a distance by the odour of gases, especially of the sulphuretted
hydrogen, they emit. Now, oxygen decomposes this gas, and thus it is
not so dangerous as represented to live near waters impregnated with
it; but should mud or vegetable refuse be left exposed by the drying up
of the waters, this gas ascends wherever the decayed matter is renewed
or turned over. Venice, Amsterdam, and other great cities similarly
situated, are not unhealthy, although their canals abound with mud;
but so soon as the traffic ceases or becomes trifling, a mud odour
arises, originating in what the French call _epuration_ or _floraison
d’eau_. In every country where there are ponds, canals, or ditches,
this vegetable growth takes place so soon as the temperature of the
water reaches 60° Fahr. As the quickening of the plants extends from
above downwards, from the leaves and stalk towards the roots, these
expand, and the mud becomes loosened; the plants imbibe carbon and give
out oxygen, and this circulation contributes to the loosening and to
the rising of the mud along with the plant. I have witnessed several
square yards of mud raised in this way from the bottom of the waters.
It subsides, of course, in due time.
We have seen that the vital force has no influence upon the combination
of the simple elements, as such, into chemical compounds. “No element
of itself is capable of serving for the nutrition and development of
any part of an animal or vegetable organization;” the vital force by
its influence merely combines inferior groups of simple atoms into
atoms of a higher order.
How stands it with the decomposition of animal and vegetable bodies
when the influence of the vital and conservative power has been
withdrawn? Let us attend to what an illustrious chemist has said on
this subject:--“Universal experience teaches us, that all organized
beings after death suffer a change, in consequence of which their
bodies gradually vanish from the surface of the earth. The mightiest
tree, after it is cut down, disappears, with the exception, perhaps,
of the bark, when exposed to the action of the air for thirty or forty
years. Leaves, young twigs, the straw which is added to the soil, juicy
fruits, &c., disappear much more quickly. In a still much shorter time
animal matters lose their cohesion; they are dissipated in the air,
leaving only the mineral elements which they had derived from the
soil.” “This grand natural process of the dissolution of all compounds
formed in living organisms begins immediately after death, when the
manifold causes no longer act, under the influence of which they were
produced. The compounds formed in the bodies of animals and of plants
undergo in the air, with the aid of moisture, a series of changes, the
last of which are the conversion of their carbon into carbonic acid,
of the hydrogen into water, of their nitrogen into ammonia, of their
sulphur into sulphuric acid. Thus their elements resume the form in
which they can again serve as food for a new generation of plants and
animals. Those elements which had been derived from the atmosphere,
take the gaseous form, and return to the air; those which the earth
had yielded return to the soil. Death, followed by the dissolution of
the dead generation, is the source of life for a new one. The same
atom of carbon which is a constituent of a muscular fibre in the heart
of a man, assists to propel the blood through his frame, was perhaps
a constituent of the heart of one of his ancestors; and any atom of
nitrogen in our brain has perhaps been a part of the brain of an
Egyptian or of a negro. As the intellect of the men of this generation
draws the food required for its development and cultivation from the
products of the intellectual activity of former times, so may the
constituents or elements of the bodies of a former generation pass
into and become part of our own frames.” “The proximate cause of the
changes which occur in organized bodies after death, is the action of
the oxygen of the air on many of their constituents. This action only
takes place when water--that is, moisture--is present, and a certain
temperature is required for its production.”
Let us not, then, be surprised at the seemingly discordant results
arrived at, and at the contradictory observations which have been
made in the best faith possible, and with every regard to truth in
science. The circumstances which seemed to be identical are merely
analogous, but in point of fact are essentially distinct, as proved
by the results. Changes inappreciable by human sense and as yet by
philosophical instruments, may and no doubt do effect results, to man
seemingly contradictory, simply because he comprehends them not. As
chemical science makes progress, these differences are being reconciled
and understood. Thus, as mere temperature exercises a truly remarkable
influence over the nature of the products of fermentation, may it not
be the efficient cause of the difference we observe between the malaria
of the delta of the Mississippi and that floating near the muddy banks
of the Scheldt? The juice of carrots, beet-root, or onions, which is
rich in sugar, when allowed to ferment at ordinary temperature yields
the same products as grape-sugar, but at a higher temperature the whole
decomposition is changed--there is a much less evolution of gas, and no
alcohol is formed.
In the fermented liquor there is no longer any sugar, and thus may it
be in the great laboratory of nature; the product of the fermentation
will assume in one locality a character it does not possess in another.
The elements are the same; there is merely a change in temperature.
Are there facts to prove that certain states of transformation or
putrefaction in a substance, are likewise propagated to parts or
constituents of the living animal body? Such facts exist. On no other
principle but that of assimilation can we explain the phenomena of
poisoning by the puncture of the living hand in dissecting-rooms, the
instrument being impregnated with a fermentescible and putrefactive
substance, there undergoing a decomposition. Similar, unquestionably,
must be the action of animal poisons, such as that of poisonous
substances, whether animal or vegetable, of the poisons giving rise
to zymotic diseases, &c.; and such may be the origin of the fevers
caused by the unknown principle which must still be connected with
the decomposition of organic bodies most frequently found in marshy
countries. But before entering more fully on this important matter,
I shall first weigh the evidence for and against a theory long
fashionable, and which may even now have its supporters--namely,
whether fermentation or the revolution of higher or more complex
organic vegetable into less complex compounds, be the effect of the
vital manifestations of vegetable matters, and whether putrefaction or
the same change in animal substances be determined by the development
or the presence of animal beings. They who maintain this theory, assume
as a natural consequence of the views that the origin of miasmatic or
contagious diseases, in so far as they may be referred to the presence
of putrefactive processes, must be ascribed to the same or to similar
causes.
§ 2. The refutation of this view by Liebig seems satisfactory, and has
not yet been satisfactorily replied to. The subject is one of much
interest; the theory has furnished a foundation for some unquestionably
entirely fallacious ideas concerning the essence of the vital processes
generally, of many pathological conditions, and the causes of certain
diseases.
These persons regard fermentation, or the resolution of higher or
more complex organic vegetable atoms into less complex compounds,
as the effect of the vital manifestations of vegetable matters; and
putrefaction, or the same change in animal substances, as being
determined by the development or the presence of animal beings.
They assume as a natural consequence of this view, that the origin
of miasmatic or contagious diseases, in so far as referrible to the
presence of putrefactive processes, must be ascribed to the same or
similar causes.
The most obvious and important considerations in support of this view
of fermentation, are derived from observations made on the alcoholic
fermentation, and on the yeast of beer and of wine. The microscopic
researches of physiologists and botanists have demonstrated that beer
or wine yeast consists of single globules strung together, which
possess all the properties of living vegetable cells, and resemble very
closely certain of the lower family of plants, such as some fungi and
algæ.
In fermenting vegetable juices, we observe, after a few days, small
points, which grow from within outwards; and these have a granular
nucleus, surrounded by a transparent envelope. The simultaneous
appearance of the yeast-cells and of the products of decomposition
of the sugar, is the chief argument in support of the opinion that
the fermentation of sugar is an effect caused by the vital process,
a result of the development, growth, and propagation of these low
vegetable structures. But if the development increase, and propagation
of these vegetable cells or tissues be the cause of fermentation, then
in every case where we observe this effect we must suppose that the
causes or conditions--namely, sugar, from which the cell-walls are
produced, and gluten, which yields their contents--are both present.
Now, the most remarkable fact among the phenomena of fermentation,
and that which must chiefly be kept in view in the explanation of the
process, is this, that the ready-formed cells, after being washed,
effect the conversion of pure cane-sugar into grape-sugar, and its
resolution into a volume of vapour and alcohol, and that the elements
of the sugar are obtained without any loss in these new forms; that
consequently, since three pounds of yeast, considered in the dry state,
decompose two hundred-weight of sugar, a very powerful action takes
place, without any notable consumption of matter for the vital purpose
of forming cells. If the property of exciting fermentation depended on
the development, propagation, and increase of yeast-cells, these cells
would be incapable of causing fermentation in pure solutions of sugar,
in which the other conditions necessary for the manifestation of the
vital properties, and especially the nitrogenous matters necessary for
the production of the contents of the cells, are absent.
Experiment has proved that in this case the yeast-cells cause
fermentation, not because they propagate their kind, but in consequence
of the decomposition of their nitrogenous contents, which are
resolved into ammonia and other products--that is, in consequence of
a decomposition which is exactly the opposite of an organic formative
process. The yeast, when brought into contact successively with the
new portions of sugar, loses by degrees entirely its power of causing
fermentation, and at last nothing is left in the liquid but its
non-nitrogenous envelopes or cell-walls.[28]
[28] Liebig: Letters on Chemistry.
On the other hand, it may be admitted that fungi and agarics, and
all that lives, vegetable and animal, contaminate the air when dead;
they absorb oxygen and give out vapours of which some are clearly
detrimental to human life. The effect of breathing air so contaminated
is in some countries immediate--that is, the incubation of the poison
requires only a few days, in others many months. Waters in a state of
fermentation or putrefaction seem to poison the plants themselves, for
duckweed and other swimming plants die, and the swallow and the marten
disappear. On the wide ocean and over the absolute desert, the air is
always pure, nothing living is decomposing; but watch the mud coasts,
and observe the pestilential effects of sea water when suffered to
evaporate, or still more when confined to a locality and suffered to
decompose. In the ancient world, as in the modern, nature teemed with
life, since a cubic inch of the fossil infusoria, contains 41,000
millions of individuals. The microscopic shell fish called entomostraca
were equally abundant.
When the evaporation of sea water is quickened by an elevation of
temperature, as in the South of France, noxious and unpleasant
odours, injurious to vegetable life, are distinctly perceptible. The
putrescence and fermentation caused by heat acting on the remains of
life in sea water left to evaporate, as between Rio and Cape Frio, in
the Brazils, seem to be the cause of, or at least to give terrible
effect to, yellow fever.
Vegetable life is equally abundant, and it may be as injurious when
decomposing in its effects on human life. Lichens speedily cover the
walls of neglected houses, and cause sickness by their decomposition.
The spore or sporule, which in flowerless plants performs the office
of seeds, floats in the atmosphere, and seems to be the cause of
the hay-fever so frequent in fertile lowlands. Nor need we quote
the recent drainage of the Lake of Haarlem in proof of the sure
results of exposing masses of dead animal and vegetable substances
to putrefaction--namely, ague, various fevers, and other ailments
indicative of a poison or malaria affecting the general mass of the
blood. Of the minuteness of animal life, it is only necessary to remark
that we are acquainted with animals possessing teeth and organs of
motion, which are wholly invisible to the naked eye. Other animals
exist which, when measured, are found to be many thousand times
smaller, and which nevertheless possess the same apparatus. Their ova
must be many hundreds of times still smaller. It is to this invisible
world in all probability, and to its decomposition and putrefaction,
or at least to influences arising therefrom, that the essential cause
of ague, and other febrile diseases of an intermittent and remittent
character may be referred, aggravated, no doubt, by insalubrious
atmospheric constitutions of which we know nothing. These from time to
time affect and lower human vitality--a fact admitted by all physicians.
* * * * *
NOTE ON THE QUESTION OF QUARANTINE. (See Chapter IV.)
The special-pleaders who formed the Council of the late Board of
Health argued that, “as there exists an obvious harmony between our
physical and social constitutions, the necessity of intercourse
between all the members of the human family is one of the final
necessities of our race” (“Report on the Quarantine Laws,” Board of
Health, p. 64); in other words, that “the diseases supposed to be
contagious by our predecessors, _cannot be contagious_, because such
a supposition is at variance with _a theory (of their own invention)_
that there exists a necessity of intercourse between all the members
of the human family;” and therefore all quarantine laws ought to be
abolished. But are not small-pox, measles, scarlatina, hooping-cough
contagious? And as regards “the necessity of intercourse between all
the members of the human family,” were we to consult the Chinese,
the Hindoo, the Peruvian, the Mexican, the Caffre, the Negro, the
Turk, the Morocene, they would unhesitatingly tell you that such an
intercourse is sure to end in their destruction. Under a Trajan or
an Alexander, an Antonine, or even an Augustus, the world no doubt
was benefited by an universal intercourse between all the members of
the human family _then known_, and such an intercourse was highly
beneficial to humanity; but the kind of intercourse established by
the Clives and Pizarros is of a very different nature from that of
Alexander and Trajan. Civilization is the direct result of artificial
wants, the gratification of which can alone be met by a free and
unrestricted commerce. By violence an empire may be overthrown,
and by rapacity its inhabitants may be deprived, not only of their
land and property, but even of their natural rights as men, as in
India under the administration of England; but all these crusades
have no reference whatever to an ameliorating of the condition of
mankind; they simply form episodes in the history of the human
race, respecting which historians take extremely different views.
The conquests of Mexico and Peru and India form episodes in the
respective histories of Spain and Britain by no means flattering to
the character of these nations.