1074. _Why has the mole hard and flat feet, armed with sharp nails?_
Because the animal is thereby enabled to _burrow in the earth_, in
search for worms. Its feet are so many _shovels_.
1075. _Why is the mole's fur exceedingly glossy and smooth?_
Because its smoothness enables it to work under ground _without the
soil sticking to its coat_, by which its progress would be impeded.
From soils of all kinds, the little worker emerges shining and clean.
[Verse: "I know all the fowls of the mountains, and the wild beasts
are mine."--PSALM L.]
What I have always most admired in the mole is its _eyes_. This
animal occasionally visiting the surface, and wanting, for its
safety and direction, to be informed when it does so, or when it
approaches it, a perception of light was necessary. I do not know
that the clearness of sight depends at all upon the size of the
organ. What is gained by the largeness or prominence of the globe
of the eye, is width in the field of vision. Such a capacity would
be of no use to an animal which was to seek its food in the dark.
The mole did not want to look about it; nor would a large advanced
eye have been easily defended from the annoyance to which the life
of the animal must constantly expose it. How indeed was the mole,
working its way under ground, to guard its eyes at all? In order
to meet this difficulty, the eyes are made scarcely larger than
the head of a corking-pin; and these minute globules are sunk so
deeply in the skull, and lie so sheltered within the velvet of
its covering, as that any contraction of what may be called the
eyebrows, not only closes up the apertures which lead to the eyes,
but presents a cushion, as it were, to any sharp or protruding
substance which might push against them. This aperture, even in
its ordinary state, is like a pin-hole in a piece of velvet,
scarcely pervious to loose particles of earth.--_Paley._
[Illustration: Fig. 70.--ELEPHANTS DRINKING.]
1076. _Why has the elephant a short unbending neck?_
Because the elephant's head is so heavy, that it could not have been
supported at the end of a long neck (or lever), without _a provision of
immense muscular power_.
[Verse: "Be not afraid, ye beasts of the field: for the pastures of
the wilderness do spring, for the tree beareth her fruit, the fig-tree
and the vine do yield their strength."--JOEL II.]
1077. _Why has the elephant a trunk?_
The trunk of an elephant _serves as a substitute for a neck_, enabling
the animal to crop the branches of trees, or to raise water from the
stream.
1078. _Why do the hind legs of elephants bend forward?_
Because the weight of the animal is so great, that when it lay down it
would _rise with great difficulty_, if its legs bent outward, as do the
legs of other animals. Being bent _under the body_, they have a greater
power of pushing directly upward, when the powerful muscles of the
thighs straighten them.
According to Cuvier, the number of muscles, in an elephant's
trunk, amounts to _forty thousand_, all of which are under the
will, and it is to these that the proboscis of this animal owes
its flexibility. It can be protruded or contracted at pleasure,
raised up or turned to either side, coiled round on itself or
twined around any object. With this instrument the elephant
collects the herbage on which he feeds and puts it into his mouth;
with this he strips the trees of their branches, or grasps his
enemy and dashes him to the ground. But this admirable organ is
not only adapted for seizing or holding substances of magnitude;
it is also capable of plucking a single leaf, or of picking up a
straw from the floor. The orifices of the canals of the extremity
are encircled by a projecting margin, produced anteriorly into
a finger-like process endowed with a high degree of sensibility
and exceedingly flexible. It is at once a finger for grasping and
a feeler: the division between the two nasal orifices or their
elevated sides serves as a point against which to press; and thus
it can pick up or hold a small coin, a bit of biscuit, or any
trifling thing with the greatest ease.--_Knight's Animal Kingdom._
1079. _Why have bats hooked claws in their wings?_
Because bats are almost destitute of legs and feet; at least those
organs are included in their wings. If they alight upon the ground,
they have great difficulty in again taking to the wing, as they cannot
run or spring to bring their wings in action upon the air. At the angle
of each wing there is placed, therefore, a bony hook, by which the bat
attaches itself to the sides of rocks, caves, and buildings, laying
hold of crevices, joinings, chinks, &c.; and when it takes its flight,
_it unhooks itself, and its wings are at once free to strike the air_.
1080. _Why does the bat fly by night?_
Because it lives chiefly upon moths, which are _night-flying insects_.
[Verse: "So are the paths of all that forget God; and the
hypocrite's hope shall perish: Whose hope shall be cut off, and whose
trust shall be a spider's web."--JOB VIII.]
1081. _Why does the bat sleep during the winter?_
Because, as the winter approaches, the moths and flying insects upon
which it feeds, disappear. _If, therefore, it did not sleep through the
winter it must have starved._
[Illustration: Fig. 71.--BAT WITH HOOKED WINGS.]
1082. _Why has the spider the power of spinning a web?_
Because, as it lives upon flies, but is _deficient of the power of
flying in pursuit of them_, it has been endowed with an instinct _to
spread a snare to entrap them_, and with the most wonderful machinery
to give that instinct effect.
There are few things better suited to remove the disgust into
which young people are betrayed on the view of some natural
objects, than this of the spider. They will find that the most
despised creature may become a subject of admiration, and be
selected by the naturalist to exhibit the marvellous works of the
creation. The terms given to these insects, lead us to expect
interesting particulars concerning them, since they have been
divided into vagrants, hunters, swimmers, and water spiders,
sedentary, and mason-spiders; thus evincing a variety in their
condition, activity, and mode of life; and we cannot be surprised
to find them varying in the performance of their vital functions
(as, for example, in their mode of breathing), as well as in
their extremities and instruments. Of these instruments the most
striking is the apparatus for spinning and weaving, by which they
not only fabricate webs to entangle their prey, but form cells for
their residence and concealment; sometimes living in the ground,
sometimes under water, yet breathing the atmosphere. Corresponding
with their very singular organisation are their instincts. We are
familiar with the watchfulness and voracity of some spiders, when
their prey is indicated by the vibration of the cords of their
net-work. Others have the eye and disposition of the lynx or
tiger, and after couching in concealment, leap upon their victims.
Some conceal themselves under a silken hood or tube, six eyes only
projecting. Some bore a hole in the earth, and line it as finely
as if it were done with the trowel and mortar, and then hang it
with delicate curtains. A very extraordinary degree of contrivance
is exhibited in the trap-door spider. This door, from which it
derives its name, has a frame and hinge on the mouth of the cell,
and is so provided that the claw of the spider can lay hold of
it, and whether she enters or goes out, says Mr. Kirby, the door
shuts of itself. But the water-spider has a domicile more curious
still: it is under water, with an opening at the lower part for
her exit and entrance; and although this cell be under water, it
contains air like a diving-bell, so that the spider breathes the
atmosphere. The air is renewed in the cell in a manner not easily
explained. The spider comes to the surface; a bubble of air is
attracted to its body; with this air she descends, and gets under
her cell, when the air is disengaged and rises into the cell; and
thus, though under water, she lives in the air. There must be some
peculiar property of the surface of this creature by which she can
move in the water surrounded with an atmosphere, and live under
the water breathing the air.
[Verse: "The spider taketh hold with her hands, and is in king's
palaces."--PROVERBS XXX.]
[Illustration: Fig. 72.--WEB OF THE GEOMETRICAL SPIDER.]
The chief instrument by which the spider performs these wonders is
the spinning apparatus. The matter from which the threads are spun
is the liquid contained in cells; the ducts from these cells open
upon little projecting teats, and the atmosphere has so immediate
an effect upon this liquid, that upon exposure to it the secretion
becomes a tough and strong thread. Twenty-four of these fine
strands form together a thread of the thickness of that of the
silk-worm. We are assured that there are three different sorts of
material thus produced, which are indeed required for the various
purposes to which they are applied--as, for example, to mix up
with the earth to form the cells; to line these cells as with fine
cotton; to make light and floating threads by which they may be
conveyed through the air, as well as those meshes which are so
geometrically and correctly formed to entrap their prey.--_Note by
Lord Brougham to Paley's Natural Theology._
[Verse: "For every beast of the forest is mine, and the cattle upon
a thousand hills."--PSALM L.]
1083. _Why have many insects a great number of eyes?_
Because the orb of the eye is fixed; there is therefore placed over
the eye a multiple-lens, which conducts light to the eye from every
direction; so that _the insect can see with a fixed eye as readily as
it could have done with a movable one_. As many as fourteen hundred
eyes, or inlets of light, have been counted in the head of a drone-bee.
The spider has _eight eyes_, mounted upon different parts of the head;
two in front, two in the top of the head, and two on each side.
1084. _Why have birds of prey no gizzards?_
Because their food _does not require to be ground_ prior to digestion,
as does the food of grain-eating birds.
1085. _Why have earth worms no feet?_
Because the undulatory motion of their muscles serves them for fill the
purposes of progression _needed by their mode of life_.
1086. _Why have mussels strong tendinous threads proceeding from their
shells?_
Because as they live in places that are beaten by the surf of the sea,
they _moor their shells_ by those threads to rocks and timbers.
1087. _Why have cockles stiff muscular tongues?_
Because, having no threads to moor themselves, as the mussels have,
they _dig out with their tongues a shelter for themselves in the sand_.
1088. _Why do oxen, sheep, deer, &c., ruminate?_
Because they have no front teeth in the upper jaw, the place of which
is occupied by a hardened gum. The first process, therefore, consists
simply of _cropping_ their food, which is passed into the paunch, to
_be brought up again and ground by the back teeth_ when the cropping
process is over.
Because, in a wild state, they are constantly exposed to the attacks
of carnivorous beasts, and as the mastication of the large amount of
vegetable food required for their sustenance would take a considerable
time, they are provided with stomachs, by which they are enabled to
fill their paunches quickly, and then, retiring to a place of safety,
they bring their food up again, and chew it at leisure.
[Verse: "A righteous man regardeth the life of his beast: but the
tender mercies of the wicked are cruel."--PROVERBS XII.]
1089. _Why can ruminating animals recover the food from their paunches?_
Because they have a _voluntary power_ over the muscles of the throat,
by which they can bring up the food at will.
1090. _Why can they keep the unchewed food in the paunch, from the
"cud" they have chewed for nourishment?_
Because their stomachs are divided into three chambers: 1, the
_paunch,_ where the unchewed food is stored; 2, the _reticulum_, where
portions of the food are received from the paunch, and moistened and
rolled into a "cud," to be sent up and chewed; and 3, the _psalterium_,
which receives the masticated food, and continues the process of
digestion.
In quadrupeds the deficiency of teeth is usually _compensated_
by the faculty of rumination. The sheep, deer, and ox tribe, are
without fore-teeth in the upper jaw. These ruminate. The horse
and ass are furnished with teeth in the upper jaw, and do not
ruminate. In the former class, the grass and hay descend into the
stomachs nearly in the state in which they are cropped from the
pasture, or gathered from the bundle. In the stomach, they are
softened by the gastric juice, which in these animals is unusually
copious. Thus softened and rendered tender, they are returned a
second time to the action of the mouth, where the grinding teeth
complete at their leisure the trituration which is necessary;
but which was before left imperfect. I say, the trituration
which is necessary; for it appears from experiments, that the
gastric fluid of sheep, for example, has no effect in digesting
plants, unless they have been previously masticated; that it only
produces a slight maceration, nearly as common water would do in
a like degree of heat; but that when once vegetables are reduced
to pieces by mastication, the fluid then exerts upon them its
specific operation. Its first effect is to soften them, and to
destroy their natural consistency; it then goes on to dissolve
them, not sparing even the toughest parts, such as the nerves of
the leaves. I think it very probable, that the gratification also
of the animal is renewed and prolonged by this faculty. Sheep,
deer, and oxen, appear to be in a state of enjoyment whilst they
are chewing the cud. It is then, perhaps, that they best relish
their food.--_Paley._
[Verse: "I am like a pelican of the wilderness: I am like an owl
of the desert. I watch, and am as a sparrow alone upon the house
top."--PSALM CII.]