Do you remember of my talking of the _vertebral column_ when I was
describing that great artery, the _aorta_, to which it forms a rampart
of defence? I should not have named it without explanation, but that you
had only to pass your hand down your back to find out what it was. Now
the _vertebral column_, or backbone, is one of those _dominant
characters_ which always carries along with it a train of other points
of resemblance in the animals where it is found. It has been chosen,
therefore, as the rallying-point of the first great group. I must tell
you beforehand that there are four of these groups, four large
companies, _i.e._, which naturalists have called by various names; as
Groups, Sections, Primary Divisions and even Branches; in this case
comparing them to four great branches of a tree, going off in different
directions from the same trunk.
And, first of all, we have to begin with the group of the
_Vertebrata_--vertebrata animals--vertebrata being a word which
explains itself.
Of course we ourselves belong to this group. In fact, we are at the
head of it; but it descends far below us. It goes on to the frog and
the fish, and includes the monkey, the ox, the fowl and the lizard;
for all these creatures possess the vertebral column. The frog does
not appear to be very much like us at first sight; and yet, by virtue
of its vertebra, it has its points of resemblance to us, which are
worth the trouble of considering. Vertebrated animals are all furnished
with a head, containing a brain, which gives its orders to the whole
body; they have all an internal skeleton, that is to say, a system of
bones linked together, forming a solid base by which all the organs
are supported. I was going to add that they have all four limbs; but
here the serpent glides in to call me to order, and to hiss at our
childish craving for fine-drawn divisions, in perfect order, where
there is an exactly proper place for everything. However, each has,
without exception, a heart, with its network of blood-vessels; red
blood, under its two conditions of arterial and venous; and also a
digestive tube, acting, on the whole, pretty much like our own. I do
not insist, mind, upon this last point, viz., that of the digestive
tube; for we shall see, by-and-by, that it is a character beyond the
pale of the primary groups. It is the fundamental character of the
trunk itself, which necessarily exists, therefore, in all the groups;
and, as I told you in my first letter, you will find it everywhere.
This is--to let you into the secret at once--the theme on which the
Great Composer has based all His infinite varieties of animal life;
and herein lies the uniformity of the animal creation, that startling
uniformity which has given so much offence to many learned men, and
which is so obvious that it will strike you of itself, I feel sure.
But I reserve this subject to the end of my letters, when you will
have heard all, and be able to judge for yourself.
It would be plunging back into confusion to attempt to examine all the
vertebrated classes at once. After making a division you must go on.
The groups have, therefore, been subdivided into _five classes_, which
we will study in succession, only naming each now: viz. _mammals_,
_birds_, _reptiles_, _fish_, and _batrachians_. Do not alarm yourself at
this last name: it is a Greek word, meaning simply frogs.
The mammals are our immediate neighbors. Mammalia are the animals which
produce milk. They bring forth their young alive, and give suck to
them as soon as they are born. This was your first nourishment, my
dear child, so you yourself are a little mammal.
What I said to you in the last letter about the horse, applies pretty
nearly as well to all mammals. We shall not, therefore, have any great
variations to notice here. Nevertheless, as these are the animals which
interest us most nearly, as they are in fact our nearest of kin, so
to speak, and those with whom we have the most to do, we will now pass
in review the different orders of which their class is composed. I
must explain to you that the _classes_ are subdivided into
_orders_, the orders into _families_, the families into
_genera_, the genera into _species_; as in armies divisions
subdivide into regiments, regiments into battalions, &c. It became
necessary, moreover, to make use of special names, in order to make
these subdivisions comprehensible, and the following are those which
have been adopted.
ORDER 1. _Bimana (two-handed)_.
Here we may pass on at once, for we have discussed this order enough
already. We are _bimane_ ourselves, since we have the distinction
of possessing two hands. Yes; that is the pretty title which the
professors have been so polite as to give us, instead of leaving us
simply our proper name of man. Yet it would have been very easy to do
this, seeing that we are the only family, the only genus, and the only
species of the order. In railway travelling, people of distinction
have a reserved carriage to themselves: so we decidedly deserve an
order to ourselves; but that is not quite the same as a separate
kingdom. In short, you are a _bimane_; so make the best you can of it.
ORDER 2. _Quadrumana (four-handed)_.
These, as their name indicates, have four hands: two at the end of the
arms, and two at the end of the legs; such are the monkeys. There is
nothing to remark; they are all alike. Stay; I am wrong, though: there
is something, insignificant it is true, but still pointing to deviation.
In some the canine teeth are set forward, _i.e._ project, and are
longer than the rest, and some species, as the ape, for instance, have
just under their cheeks convenient little pockets, which open into the
mouth, and in which they can deposit a reserve of nuts to be devoured
at leisure; these are called _pouches_.
It is a trifle in itself, but we have here a first example of the
eccentricities of nature in the construction of animals. At one time
she adds a detail; at another she suppresses one. Sometimes she is
pleased to enlarge an organ, as in the canine teeth of the monkey;
sometimes she reduces it; or perhaps here she makes its construction
more simple; there again more complicated: but still it is always the
same organ. So the dressmaker shapes the sleeves of a dress, sometimes
open, sometimes closed, flat or puffed, plain or ornamented,
pagoda-shaped or gigot-formed: but still they are all of them sleeves.
ORDER 3. _Cheiroptera (wing-handed)_.
I am quite ashamed of offering you such a word as this, my dear child.
It was a Greek fancy of the learned men, who would not condescend to
use the vulgar name Bats. In the Greek, _cheir_ means hand, and
_pteron_ wing. The Cheiroptera are animals with winged hands; in
fact, the fingers which terminate the fore-limbs of the bat lengthen
as they spread out to an extravagant extent; and are connected together
by a membrane springing from the body, with which they beat the air
as with a wing, and which enables them to fly with such ease that
theyare often taken for birds.
But, so far from really being a bird, this curious little creature has
the same internal organization as ours, and indeed comes so near us,
though without looking as if it did, that a scientific man, and a very
distinguished one too, placed the bat in the first family of the animal
kingdom, with the monkey, and, you will hardly believe it, with man.
It is found that the bat, like man and the monkey, suckles its young
at the breast; and it was this very character which Linnæus, the leader
of artificial classification, thought of selecting as the distinguishing
mark of his first family in the animal kingdom. It is true that in
honor of the human race he had given that first family a much more
sonorous name than our usual one of _man_--viz. _primates_, the first in
rank--that is, the princes. But, alas! we were to be princes on an
equality with bats; and, for my own part, I prefer being a _bimane_, and
alone. I really believe that it was to put this saucy little creature
back into its proper place that, at the time of the great revolution in
favor of natural classification, the conclave of professors assembled at
the Botanical Gardens in Paris inflicted this horrid name of Cheiroptera
on the bat, ejecting it contemptuously from the overthrown dynasty of
the _primates_.
I have not been sorry to make you acquainted as we went along, with
this little trait in the history of classification; but beyond it there
is really nothing particular to say about the apparatus for the
nourishment of the deposed bat-princes, which is a plain proof how
nearly it must be like our own. By-the-by, there is one trifling remark
to be made with regard to her teeth. The bats we have in our country
(France), for there are many varieties of species in the world, live
on insects, which they catch in their flight by night. These insects
are often enveloped in a very hard outer case, which molars like ours
would have some difficulty in chewing properly; consequently the molars
of our little friend are fringed with conical points, and with these
she grinds down her prey without difficulty.
In America there is a large bat, the vampire, which lives on the blood
of animals, and nature has armed it accordingly. It has at the
extremityof its muzzle two sharp beak-like incisors, like the lancets of
a surgeon. The vampire bat, which roams by night like other bats, goes
straight at the large animals it sees asleep, delicately opens a vein
in the throat without waking them, and sucks their blood in long
draughts, taking care, by fanning them with its wings, to lull them
into a cool and balmy slumber. It does not, as you see, make a savage
attack on its victim: it merely inflicts a bite like that of the leech,
but the result may be death. This is the best emblem I know of the
sycophant, who undermines your soul while he fans your vanity; and
observe, while we are on the subject, that this species has always had
the art of insinuating itself among princes.
ORDER 4. _Carnivora (flesh-eaters)_.
When translated into English, this word needs no explanation. And here
we have the tribe of bears, wolves, foxes, weasels, dogs, cats, tigers,
lions, of all the fighting animals, _i.e._, those which steep
their muzzles in blood, and live by devouring others. These have a
similar apparatus for nutrition to our own; especially the bear, who,
with the monkey, is the animal most nearly resembling man, seeing that
he has feet like ours, with scarcely any tail, while the monkey has
our hands, without specifying any other points of resemblance. Like
ourselves, too, the bear is omnivorous; that is to say, it eats
everything, vegetables and fruit as well as meat; and nature, which
has given it our diet, has furnished it with molars almost exactly
like our own. Its canine teeth alone differ from ours: they are more
prominent even than those of the _quadrumana_; and this is the
case with all the members of the order, in whom we find them sometimes
developed into actual daggers. But those of them which are purely
carnivorous have molars peculiar to themselves. The lion, for example,
who does not share the bear's taste for carrots, and who would die of
hunger surrounded by the honey and grapes of which the bear is so
fond--the lion, who never takes anything but raw meat between his
teeth, has molars furnished with sharp cutting edges, intended to slice
the meat like the chopping knives used by cooks for making a hash.
The lion offers another peculiarity, which is common to him with all
the _Carnivora_. Place your finger close to the lower end of your
ear, and work your jaw; you will feel something hard moving backward
and forward against your finger. This is where the lower jaw is set
into a bone of the skull, called the _temporal_, if you care to know its
name; in other words, the bone of the temple. The extremity of the jaw
bends, and forms a kind of little knob, called _condyle_, which fits
into a cavity of the temporal bone. With us the cavity is not very deep,
nor the knob very large, so that it can play very freely; and it is this
which allows us that second movement from side to side, of which I spoke
to you formerly, and thanks to which, our little mills reduce a mouthful
of bread into paste. But this freedom of action has also its
inconveniences. You must never attempt to force too large an article
into your mouth at once--an apple, for instance--the efforts you would
then be obliged to make might easily cause the _condyle_ to slip out of
its little cavity, where its hold is but slight, and to get under the
_temporal bone_; and there you would be with your mouth wide open until
the doctor arrived. The lion, whose voracious jaw opens like the door of
an oven, so that the tamers of wild beasts have no scruple in thrusting
in their whole heads, a mouthful a good deal larger than an apple; the
lion, who has no doctors, would often be liable to this accident--an
irremediable one in his case--if nature had not made a special provision
for him. In order to secure greater firmness and strength, the second
movement is in his case sacrificed by embedding the _condyles_
deeply in their cavities, where they are fastened in such a fashion
that they can only move up and down, like the handles of a pair of
pincers. This is a restraint which enables the jaw to be safely thrown
open as wide as the fiery impulse of its terrible proprietor impels
it. Less freedom, in exchange for more power, is a bargain which any
one would gladly accept who plays the part of a lion!
I have here a remark to make. We have now passed in review three orders
besides our own, and have only had to point out a change in the
fastenings of the jaws and in the teeth; and you will find that the
same sort of modifications take place in the whole class of mammals.
This is in fact the essentially movable and variable point in their
apparatus for nutrition. The jaw and its weapons vary their character
from one species to another, according to the nature of their food;
but the modifications generally terminate there, _i.e._ on the
threshold, as it were. The interior arrangements of the house remain
otherwise much the same in all.
Here, however, in the lion, there is an interior change to be described;
but not in the arrangement of the parts, only in their size; the stomach
in this species being even smaller and weaker in proportion than ours,
and the digestive tube more than twice as short. The digestive tube
of an ordinary sized man is about seven times the length of his body,
whilst that of the lion only measures three times the length of the
animal. This is a natural consequence of the kind of nourishment he
takes. Flesh and blood, on which he lives entirely, is concentrated
_albumen_, prepared beforehand in the bodies of his victims; so
that no great preparation is needed here to convert it into lion's
blood. A professor of chemistry, who has a good assistant, does not
need a very large laboratory. This is the case with the lion; and
nature, which makes nothing in vain, has here economised space. Tame
the monarch of the forest into a domestic animal, and change his food,
and I will wager anything you please that, in the course of a few
generations, his digestive tube will lengthen itself. Examine the
inside of the cat, his little cousin, formed originally on the same
pattern as himself, and, without having ascertained the fact myself,
I am sure that, by dint of feeding it daily on sops and milk from
generation to generation, its digestive tube has become more than three
times the length of its body.
Here you ought to be told at once a very important fact relative to
the organization of the lower animals, one which places them all very
far below the order of _Bimana_, since there is such an order.
In bestowing intelligence and freedom of action on man, the Almighty
has given him the unspeakable privilege of working in His footsteps--if
I may presume to use the expression--of following up His work of
creation as it came from His hand. Now especially that man begins to
see a little more clearly into the laws of life, he has entered more
directly into the possession of this almost divine privilege, which
the Almighty has graciously vouchsafed him. You can even now have an
ox or a sheep made to order in England, giving your dimensions, as if
you were ordering a cabinet; and in a few years, if you have not asked
actual impossibilities, your commission will be executed to within an
inch. This is not said in reference to the _Carnivora_. But in
bidding you good-bye, my dear little mammal, I could not bear to leave
you under the weight of that debasing title: I wanted also to show you
your greatness.