assigned to animals on our globe. The basis of this system, as will be
seen, is the intelligence accorded to animals. We entirely repel the
generally held opinion, that beasts do not possess intelligence, and
that it is replaced by an obscure faculty which is called instinct. But
this theory gives no reason, it merely puts a word in the place of an
explanation. By a simple phrase people imagine they resolve one of the
great problems of nature. The timid and conventional philosophy of our
time has hitherto accommodated itself to this method of eluding great
difficulties, but the moment now appears to have come for a deeper
study of the problems of nature, and for no longer remaining content
with the substitution of words for things.
There was no hesitation in ancient times about according intelligence
to animals. Aristotle and Plato expressed themselves quite clearly
on this point: they admitted no doubt of the reasoning powers of
beasts. The most celebrated modern philosophers, Leibnitz, Locke, and
Montaigne; the most eminent naturalists, Charles Bonnet, Georges Leroy,
Dupont de Nemours, Swammerdam, Réaumur, &c., granted intelligence
to animals. Charles Bonnet understood the language of many animals,
and Dupont de Nemours has given us a translation of the "_Chansons
du Rossignol_" and the "_Dictionnaire de la Langue des Corbeaux_."
It is, therefore, difficult to understand how a contrary thesis
became prevalent in this age, how Descartes and Buffon, the declared
adversaries of animal intelligence, have succeeded in turning the scale
in favour of their ideas.
Descartes regarded animals purely as machines, as automata provided
with mechanical apparatus. It would be difficult to surpass our great
philosopher in absurdity when he treats of these animal machines.[12]
_Equidem bonus dormitat Descartes._ The systematic errors of Buffon on
the same subject are well known.
The partizans of Descartes and of Buffon have popularized the idea
of instinct put in the place of intelligence, of the word replacing
the thing. But, in simple truth, what difference is there between
intelligence and instinct? None. These two words only represent two
different degrees of the same faculty. Instinct is simply a weaker
degree of intelligence. If we read the writings of naturalists
of this country who have studied the question, Frederick Cuvier
(brother to George Cuvier), and Flourens,[13] who has but commented
upon Frederick Cuvier's book on the more profound work of a learned
contemporary writer, M. Fée of Strasbourg,[14] we shall easily find
that no fundamental distinction between intelligence and instinct
can be established, and that the whole secret of our philosophers and
naturalists consists in calling the intelligence of animals, which is
weaker than ours, _instinct_.
It is, then, the pride of mankind which has attempted to place a
barrier, which in reality has no existence, between us and the animal.
The intelligence of the animal is less developed than that of the man,
because his wants are fewer, his organs are less highly finished, and
because the sphere of his activity is more limited, but that is all.
And sometimes, even, we must not forget that the animal exceeds the
man in intelligence. Look at the rude and brutal waggoner, beside
his good and docile horse, which he mercilessly beats and abuses,
while his faithful auxiliary fulfils his task with patient exactness,
and say, is it not the master who is the brute, and the animal who
is the intelligent being? In kindness--that sweet emanation of the
soul--animals often excel men. Every one knows the horrid story of the
man who carried his dog to a river to drown him, but who fell into the
water himself, and was on the point of drowning. The faithful companion
whom he had flung in to die was there; he swam to his master, and
dragged him into safety. Then the dog's master, making his footing sure
this time, seized the creature who had just rescued him, and drowned
him.
According to our system, the human soul comes from an animal belonging
to the superior orders. After having undergone, in the body of this
animal, a suitable degree of perfecting and elaboration, it incarnates
itself in the body of a newly-born child of the human race.
We said, in a former chapter, "Death is not a termination, but a
change; we do not die, we experience a metamorphosis." We must add to
this, "Birth is not a beginning, it is a consequence. To be born is not
to begin, it is to continue a prior existence."
There is not, therefore, properly speaking, either birth or death for
the human species; there is only a continuous succession of existences,
extending from the visible world through space, and connecting each
with those worlds which are hidden from our view.
[Illustration]
FOOTNOTES:
[12] This question is specially considered in Descartes' "_Discours sur
la Méthode._"
[13] "_De l'Instinct et de l'Intelligence des Animaux_," Paris, 1861.
[14] "_Etudes Philosophiques sur l'Instinct et l'Intelligence des
Animaux_," Strasbourg, 1853.
[Illustration]
CHAPTER THE TWELFTH.
WHAT IS THE PLANT?--THE PLANT IS SENSIBLE.--HOW DIFFICULT IT IS TO
DISTINGUISH PLANTS FROM ANIMALS.--THE GENERAL CHAIN OF LIVING BEINGS.
LINNÆUS has said, "The plant lives; the animal lives and feels;
man lives, feels, and thinks." This aphorism represented the state
of science in the times of Linnæus. But since the year 1778, that
is to say, since the death of the great botanist, Upsal, natural
science has progressed, botany and zoology have been enriched with
innumerable facts and fundamental discoveries, so that the Linnæan
formula no longer represents the present condition of the sciences
of organization. We believe that the following proposition may be
truthfully substituted: "The plant lives and feels; the animal and man
live, feel, and think."
To accord sensibility to plants, is to transgress the classic laws of
natural history, so that the considerations and facts which appear to
us to justify this proposition ought to be most carefully stated.
1. The plant feels the sensations of pleasure and pain. Cold, for
instance, impresses it painfully; it may be seen to contract itself,
as if shivering, under the influence of a sudden or excessive fall of
the temperature. An abnormal excess of temperature evidently causes
it to suffer; when the heat is very great, leaves may be observed to
hang down on the stems, curl up, and appear to wither; when the cool of
the evening comes, the leaves rise up again, and the plant resumes its
appearance of placid health. Drought also occasions manifest suffering
to plants. Those who study nature with loving attention know that when,
after a long period of drought, a plant is watered it exhibits signs of
pleasure. On the other hand, a wounded plant, one from which a branch
has been cut, appears to experience pain. A pathological liquid exudes
from the wound, like the blood from a hurt animal; the plant is sick,
and will die, if it do not receive the necessary succour. Thus persons
who love plants will not cut flowers off their stems, they prefer to
inhale their perfume, and contemplate their brilliant colours, on the
stalk, without inflicting a painful mutilation upon the beautiful
creatures which they admire.
The sensitive plant, if touched by the fingers, or even struck by a
current of harsh air, folds up its leaves, and contracts itself. The
botanist, Desfontaines, saw a sensitive plant, which he was bringing
home in a carriage, contract its leaves while the vehicle was in
motion, and expand them when it stopped, thus affording a proof that
the movement distressed the plant. A drop of acid, or acrid liquid,
placed on a leaf of a sensitive plant, will occasion a similar
constriction. All vegetables present an analogous phenomenon. Their
tissues contract when brought in contact with irritant substances. By
rubbing the tips of a lettuce, the juice may be made to exude.
Vegetable sensibility exists by the same right as animal sensibility,
since electricity kills plants as it kills animals, since narcotic
poisons kill or stupefy plants as they kill and stupefy animals. One
can narcotize a plant by watering it with opium dissolved in water, and
MM. Gopport and Macaire have discovered that hydrocyanic acid kills
plants as rapidly as animals.
2. Plants sleep at night. During the day they develop their vital
activity, and when the night comes, or when they are in darkness, their
leaves assume another position, that of repose; they fold themselves
up. In the day-time, the upper surface of the leaf is turned to the
sky, and the under surface towards the earth; this under surface,
pierced with holes, or _stomata_, is the part through which absorption
and exhalation take place, while the upper surface, in which there
are no such openings, is only a sort of screen for the protection of
the absorbing surface. It is therefore easy to understand that the
horizontal attitude of the leaves is a position of vital activity, and
that the refolding of those leaves during the night indicates a state
of repose. It is precisely the same case with ourselves, when during
the night we indulge our muscles, kept on the stretch during the day,
with complete relaxation.
The _sleep of plants_, said to have been discovered by Linnæus, and
which was certainly described for the first time in one of Upsal's
_Thèses de Botanique_, and thoroughly elucidated by Linnæus, is not a
phenomenon limited to certain families of plants. There are very few
vegetables which, during the night, or in darkness, do not fold their
leaves, and which do not present a different appearance by day and by
night. The Sensitive is the classic plant selected for its exhibition
of this phenomenon in all its intensity; but this small leguminous
creature only presents us with an exaggeration of a fact which exists
in a lesser degree among almost all vegetables with light leaves. We
may quote the following passage from a former work on the subject of
this phenomenon.
"The sleep of plants vaguely resembles that of animals. It is a
remarkable circumstance that the slumbering leaf appears to wish
to return to the epoch of its infancy. It folds itself almost as
it was when in the bud, before it burst out, as it was in the
lethargic sleep of winter, sheltered beneath its strong scales, or
wrapped up in its warm down. One would think that the plant was
trying every night to resume the position which it occupied in its
early time, just as the sleeping animal gathers himself together,
and folds his limbs as they were folded in his mother's womb."[15]
Is it possible to deny the possession of sensibility to creatures
which give us alternate sign of repose and of activity, and who have
the power of accommodating themselves to various external impressions?
Fatigue cannot possibly be anything but the consequence of the
experience of an impression.
3. Numerous physiological functions are fulfilled by plants as well
as by animals; and when we consider the number and variety of these
functions, it is difficult to understand how, if animals be, as the
common consent of mankind declares them, possessed of sensibility,
plants can be destitute of it. An ancient philosopher defined plants
as _animals with roots_. We shall see, on examining the variety of
functions performed by vegetables, whether this philosopher was not a
far-seeing, wise man.
It would be difficult to name any function with which the animal
is invested that the vegetable does not possess in a less degree.
_Respiration_, for instance, is equally a property of plants and of
animals. Among the latter, respiration consists in the absorption of
the oxygen of the air and the emission of carbonic acid gas and watery
vapour; among plants it consists in the emission of carbonic acid gas
and watery vapour during the night, and during the day, under the
influence of sunlight, of the emission of oxygen proceeding from the
decomposition of carbonic acid. The function is evidently of the same
nature in both the natural kingdoms.
_Exhalation_ is a function common to vegetables and to animals. By
the stomata of leaves, as by the pores of the skin of animals, watery
vapour and various gases, according to the vital phenomena which take
place in the interior of the tissues, are constantly being disengaged.
_Absorption_ takes place in both kingdoms. If you pour water on the
lower surface of a leaf, you will see that it will be absorbed with
great rapidity. Sprinkle a bouquet of flowers with water, and the
freshness of the withered blossoms will revive. Absorption is even more
active in vegetable than in animal tissues.
The circulation of liquids in the interior of plants is accomplished
by a complicated system of channels and vessels of every order and of
every calibre, absorbent vessels, exhalant vessels.
Nothing is more varied than the disposition of these channels in the
interior of plants, and their multiplicity indicates a circulatory
function as complicated as that of animals.
It is then evident that vegetables have the same physiological
functions as animals, but as yet we know those functions very
imperfectly. It is very strange that while animal physiology is so far
advanced in our day, vegetable physiology is almost in its infancy.
We know very well how the digestion of food takes place in man and
animals, we know how our blood circulates in a double system of
vessels, called arteries and veins, and we know the central organ, the
heart, through which the two liquids are carried by this double system.
We see and we touch the organs of sensation and motion, that is to say,
the nerves. More than this, we distinguish the nerves which produce
sensation from those which rule motion. We know that the centre of
nervous action in man and animals is double; that its seat is equally
in the brain and in the spinal marrow.
Briefly, science has shed its brightest light on all the functions
belonging to animal organization, while vegetable physiology remains in
obscurity. Notwithstanding the labours of naturalists within the last
two centuries, we cannot explain the life of plants with certainty.
We cannot positively state how the sap, which is vegetable blood,
circulates in their channels. We do not even know with precision
whether a tree grows from the outside to the inside, or from the inside
to the outside. All the physiological functions in the vegetable
kingdom are hidden from us by a thick veil, and it is only by lifting
a corner of it with great difficulty that we can catch a few gleams
of light through the obscurity. Nevertheless, all unexplained though
they be as yet, physiological functions do exist in plants. Considering
these numerous functions, it appears entirely impossible that plants
should not have received the gift of sensibility. It is difficult to
believe, as Linnæus would have us believe, that they possess life, and
nothing more.
We shall be told that vegetables have no nerves, and that in the
absence of every organ of sensation, we cannot accord them the faculty
of sensibility. But, we reply, that the imperfect state of vegetable
anatomy and physiology forbids us to come to any conclusion touching
the existence or the absence of nerves in plants. We are convinced that
these organs exist, but that botanists do not know how to discern them,
or have no means of distinguishing between them and other organs.
4. The manner of multiplication and reproduction among plants and
animals is so analogous, that it seems impossible, when we consider
this extraordinary resemblance in the most important functions, to
refuse sensibility to plants, and accord it to animals.
Let us consider the various modes of reproduction proper to vegetables.
Reproduction, or rather the fecundation which precedes it, is executed
in certain vegetables, by means of an apparatus of the same typical
form as that of the animal kingdom. It is composed of a male organ,
the stamen, which contains the impregnating dust, pollen, and of a
female organ, the ovary, supported by a stalk, the pistil. The pollen
impregnates the ovula contained in the grains of pollen in the ovary,
as the seed of the male impregnates the ovula contained in the egg of
the animal. In both cases the fruit of the impregnation develops itself
afterwards with the aid of warmth and time. The vegetable egg grows and
ripens, just as the animal egg grows and ripens.
We may add that the analogy between the modes of reproduction, in the
two kingdoms, animal and vegetable, does not limit itself to these
conditions of likeness; we may observe resemblances in the specialities
of the function. Particular vitality, a turgid state of the tissues,
accompanied by elevation of the local temperature, occur in the case
of certain plants at the moment of impregnation, especially in the
species of the family of Aroïdes. On placing a thermometer, at that
time, in the great floral covering of the Arums, an excess of from 1°
to 2° on the temperature of the surrounding air will be denoted, an
extraordinary fact in vegetable life, for vegetables are always colder
than the external air. How can we believe that the plant in which this
excitement takes place has no feeling of its own condition? The plant,
like the animal, has its seasons of love, can it be that it has no
consciousness of them? Are we to believe that the plant which becomes
warm, in which life rises at the moment of impregnation, has no more
sensation than a stone? Such is not our opinion. We cannot understand
life without sensibility--the one appears to us to be the indication of
the other.
The analogy between the plant and the animal in their functions
of reproduction is nowhere more evident or more curious than in a
vegetable production which abounds in the waters of the Rhône, and has
received the name of _Vallisneria spiralis_. In this plant the male
and female organs are placed on different branches of the same plant.
The female flowers are fixed to the ground by long, twisted, spiral
stalks. But, when seeding time comes, the spirals of the stems unroll
themselves, and the female flowers come up to the surface of the water
and spread themselves out. The male flowers, not being placed like the
female on elastic stems, cannot come up to the surface of the water.
What do they do? They burst through their covering, and float around
their females on the surface of the water. After that the current
carries away the detached male flowers; and the female stem folds
itself up again, and sinks to the bottom of the river, there to ripen
its impregnated ovules.
The function of reproduction in plants is rich in conclusions in
support of our thesis. The plants called phanerogamous are not
reproduced only by impregnation by means of the visible sexual organs,
the pistil and the stamen, they are also multiplied by grafts, buds,
and cuttings. Cryptogamous plants, which have no sexual organs,
are multiplied either by effects which detach themselves from the
individual plant at a certain period of its vegetation as we see
in the case of fungi, algæ, mushrooms, &c., or by fragments of the
individual itself, which, being thrown into the ground, germinate and
multiply themselves.
Animals, in their several classes, represent all these modes of
reproduction; there is not one which does not exist among them. Animals
are not reproduced by eggs only, either interior or exterior, and by
living young ones, they are equally multiplied, like vegetables, by
offsets, by cuttings, and by ingraftment.
Multiplication by offsets may be observed in the fresh-water polype.
Little buds which grow and lengthen come out of the body of this
animal. While the bud is lengthening, he throws off other and smaller
offsets, which throw off still smaller ones. All these are so many
little polypes, which derive their nourishment from the principal
polype. Having attained a certain size, these offsets separate
themselves from the primitive individual, and constitute so many new
polypes. Coral multiplies itself in the same manner. From the principal
branch spring secondary branches which have originated in a bud or
shoot, and these branches, inserting themselves into the chief stem,
form new individuals. Thus the exterior aspect of the coral resembles a
ramified tree rather than an animal.
Madrepores, another kind of zoophytes, resemble trees so closely, that
for centuries they were supposed to be marine plants; they too, like
coral, are reproduced by offsets.
Multiplication by cuttings is seen in the fresh-water polype. Take a
fresh-water polype, and cut it into as many fragments as you choose.
Each of these fragments, left to itself, will become a polype. These
new individuals may be in their turn cut into pieces, which will
produce as many new ones. This is multiplication by cuttings, exactly
similar to the process in plants, so that the generation of fresh-water
polypes does not differ from that of one of our fruit-trees. It is not
only the entire polype which, thus cut to fragments, furnishes a new
polype; the skin of this animal can also produce one new individual or
several. Is not this a vegetable ingraftment?
A similar generation by ingraftment is to be observed in another
instance, in the case of the fresh-water polype. Take different
portions of the same polype, or those of different polypes, and join
them at the ends, or lay them upon one another, and you will combine
them so closely that they reciprocally nourish each other, and
ultimately form only one individual. Here is vegetable ingraftment
carried out in an animal.
5. Other points of resemblance exist between plants and animals. If
they are not generally remarked, it is because the authors of the
classics of natural history do not direct the attention of the reader
to these facts. We are about to supplement their silence, and to bring
the analogies between the two natural kingdoms into view.
Firstly, there exists in both a common and equally astonishing
fecundity. Among plants, as among animals, one individual can give
birth to thousands of individuals like himself. Vegetables are even
more fertile than the superior animals. Trees produce every year, and
sometimes for a century. Mammiferous animals, birds, and reptiles
produce infinitely less than trees; their pregnancy is less frequent,
and takes place during a certain period in the life of the animal only.
The elm produces every year more than 300,000 seeds, and this may
continue for a hundred years. Fish and insects approach most nearly to
trees in fecundity. A tench spawns 10,000 eggs yearly, a carp 20,000.
Among insects, a female bee produces from 40,000 to 50,000 eggs. To
these animals we may compare, among vegetables, the poppy, the fern,
the mustard plant, which produce incalculable quantities of seeds. We
must not forget, besides, that vegetables multiply themselves in many
ways, whereas each animal possesses but one mode of reproduction.
What we wish to establish, what is evident, is that among both animals
and plants fecundity is equal, and equally prodigious. From the point
of view of this analogy, we may also quote the size of the species,
which is extremely variable in both kingdoms, because both produce at
the same time giant species and dwarf species. Among animals, there
are some of monstrous size, such as the whale, the cachalot, and the
elephant, such as the gigantic reptiles of the ancient world, the
ichthyosaurus, which was longer than the whale, the megalosaurus and
the iguanadon, which were as large as the elephant.
To these colossi of the animal kingdom, we may oppose the colossi
of the vegetable kingdom; the monstrous baobab gourd, which covers
hundreds of square yards with its shade, the elm, whose trunk may
grow to the size of a whale's girth, the _Eucalyptus globulus_, an
Australian tree which is being acclimatized in Algeria and in the south
of France, the _Sequioœa gigantea_, the giant of Californian forests.
If the two kingdoms of nature have their colossi, they have also their
dwarfs, and their infinitely little. There are cryptogamic vegetables
which are only to be seen with the microscope, and there are animalculæ
equally invisible to the naked eye. If the animal kingdom can show,
in its scale of size, the whale, and the microscopic _acarus_, the
vegetable kingdom possesses a similar decreasing scale from the baobab
to the lichens.