SPIRAL AND RINGED TISSUES.--VARIOUS SPRINGS IN NATURE AND ART.
Spiral Tissues, and their Structure and Uses.--The movable
Gas-lamp.--Elastic Tubes.--Breathing-tubes of Insects, and their
Spiral Wire.--Ringed Tissues and their varied Structure.--Ringed
Tissues applied to modern Dress.--Chinese and Japanese
Lanterns.--Proboscis of the House-fly.--Trachea of various
Animals.--Mutual Tendency of Rings and Spirals towards each
other.--Fibres of the Yew-tree.--Diving and Divers.--Principle of
the Diving-bell.--How it is supplied with Air.--Structure of the
Air-tubes.--Nests of the Water-spider.--Diving by means of
Tubes.--Larva of the Drone-fly, and its Mode of breathing.--How to
examine them.--Leaping Springs.--The Skip-jack in Nature and
Art.--Skip-jack or Click Beetles.--The Spring-tail, Grasshopper,
Kangaroo, Gerboa, and other Jumping Creatures.
SPIRAL AND RINGED TISSUES.
We have now to consider the Spiral Tissue under another aspect, _i.e._
that of acting as the internal support of an exterior membrane. Ringed
tissues are necessarily conjoined with the Spiral, as they both
discharge the same office, and in some cases merge almost imperceptibly
into each other in the same specimens. This is most beautifully shown in
the proboscis of the common House-fly, to which reference will presently
be made.
The subject is so large that only a comparatively small selection of
examples can be made, the greater number belonging to Nature, and not to
Art.
We will first take the common movable Gas-lamp, with its accompanying
tube. It is at present the tube of which we have to treat, the gas
itself being reserved for a future page.
It is necessary that, in order to enable the lamp to be moved from one
spot to another, the tube through which the gas passes must be so
constructed that if it be bent, or even coiled, it retains its form, and
does not become flattened. In order to obtain this object, a very long
thin wire is coiled spirally to a suitable length. Over this wire is
sewn the casing of the tube, which is afterwards made waterproof with
elastic varnish. A still simpler mode is by enclosing a spiral wire
within a tube of vulcanised india-rubber. It will be seen, then, that by
the elasticity of the spiral wire the tube must always retain its shape,
no matter how much it may be bent.
On the right hand of the illustration are shown the movable Gas-lamp and
tube, and a portion of the latter is given with its spiral wire
partially unwound, in order to show its structure.
[Illustration: TRACHEA OF INSECT, WITH ITS SPIRAL THREAD.]
[Illustration: TUBE OF GAS-LAMP, WITH ITS SPIRAL WIRE.]
The large tubes which convey air to divers are made in the same manner,
as they would not only succumb to the pressure of the water without the
wire, but could not be dragged over obstacles or round corners without
collapsing. It often happens that a diver is obliged, when surveying a
sunken ship, to traverse the whole of her interior, descending ladder
after ladder, and entering every cabin in the ship. This could not be
done but for the internal coil of wire within the tube. Reference will
presently be made to the subject of diving.
* * * * *
ON the left hand is seen an object that looks something like a branch
hollowed very thin. It is a magnified view of part of the Trachea or
breathing-tube through which air is conveyed into the system of an
insect. These breathing-tubes ramify to every portion of the body of an
insect, even penetrating to the extremities of the antennæ, the wings,
and the legs. It is obvious that as these organs are in tolerably
constant movement, and the legs are much bent at every joint by the
action of walking, the air-tubes which run through them must possess the
same qualities as those of the gas-lamp and diver.
If one of these tracheæ be removed and placed under the microscope, it
will be seen to be constructed in a manner exactly similar to that which
has been described. Within the membrane which forms the tube proper
there is a very fine, but very strong thread, which is coiled exactly
like the wire spring. It is not attached to the membrane, and so strong
is it that, although it is all but invisible to the naked eye, it can be
drawn out as shown in the left-hand figure of the illustration. If laid
on a piece of glass, it immediately tries to recoil itself, and for some
little time will twist and curl about as if it were alive.
[Illustration: TRACHEA OF DRAGON-FLY LARVA.]
[Illustration: TUBE OF HOOKAH.]
* * * * *
ON the above illustration are two similar examples of the spiral thread
with a flexible tube. The right-hand figure represents one of the many
forms of the water-pipe, whether known as Hookah, Narghile, or
Hubble-bubble. In the simpler forms of this pipe, such as the latter,
the inhaling-tube is quite straight, and the bowl is held in the hands
of the smoker. In the more refined pipe, however, the tube is very long,
flexible, and made elastic by an inner spiral wire.
Perhaps the reader may remember that the larva of the Dragon-fly is a
most remarkable creature in consequence of its methods of propulsion
and respiration. The water is taken into the interior of the body
through a peculiarly formed aperture, and then ejected with such
violence as to drive the body forward on the same principle as that
which causes a rocket to ascend.
The figure on the left hand of the illustration is a representation of
the abdomen of this larva rather magnified, and opened so as to show the
interior. On either side run the two principal breathing-tubes, through
the delicate membranes of which the spiral thread can plainly be seen.
These tubes are connected with a smaller set, and they with a still
smaller, so that at last they are of such tenuity that they can scarcely
be distinguished without the use of a glass. But, however small they may
be, they are always fitted with the spiral thread.
* * * * *
WE now come to the cases where the membrane is supported by a series of
rings, and not by a single spiral wire.
In the right-hand division of the illustration are two specimens of
objects which shall be nameless, but which were drawn per special favour
at a milliner’s shop. Although the day has now happily gone by when the
larger object was in general wear, and seemed to be irrepressively
increasing in dimensions, certain modifications of it, under various
names, have made their appearance in almost every book of fashions and
every large milliner’s shop.
Here we have the external membrane made of linen, calico, merino, or
similar material, distended by a number of elastic rings set at
tolerably even distances from each other.
The two small objects represent the handy little paper lanterns so
common in China and Japan. They are composed of an external coat of
tough tissue paper, so thin that it allows the light to pass through it
with tolerable freedom, and of an internal series of elastic rings,
which not only support it and preserve its cylindrical shape, but allow
it to be folded up flat when not wanted.
I possess a singularly ingenious lantern of this kind, made in Japan,
and displaying the thoroughness of work which characterizes that nation.
It is five inches in diameter, and the lantern itself is affixed at
either end to a circular wooden cap the upper fitting over the lower.
Consequently, when the lantern is shut, it is entirely enclosed between
these two caps, which effectually preserve it from harm. It is
delicately finished, and has no less than thirty rings, made of very
narrow strips of bamboo. The upper cap has a little trap-door through
which the candle can be admitted and trimmed, and in its centre is a
small round hole for the passage of air.
* * * * *
IN the left-hand division of the illustration are shown several examples
of ringed and spiral tissues belonging to the vegetable world, in which
the principle is exactly the same as that of the Chinese lantern, &c.
That on the right hand is an example of simple rings within a membrane.
The central figure shows a double spiral, which produces very much the
appearance of a series of rings; and on the extreme left is an
interesting example which shows the transition in the internal supports
from spirals to rings.
[Illustration: SPIRAL AND RINGED FIBRE (VEGETABLE).]
[Illustration: NAMELESS OBJECTS.]
[Illustration: PAPER LANTERNS.]
I have already mentioned that the proboscis of the House-fly exhibits
this modification. If one of these objects be placed under a moderate
power microscope--the half-inch is quite enough--and examined, it will
be seen that there are some large tracheæ, just like those of the
Dragon-fly larva, on each side of the proboscis, and that, where the end
is widened and flattened into a sort of disc, their place is taken by a
set of very much smaller tracheæ, coming nearly to a point, and each
being supported internally by a series of incomplete rings, shaped very
much like the letter C. A slide containing this object well mounted can
be purchased at any optician’s for a shilling.
* * * * *
THE trachea, or windpipe, as we call it, of all vertebrate animals, man
included, is formed on exactly the same principle, as any one may see by
going to a butcher’s shop, and looking at the trachea, or windpipe, by
which the lungs, or “lights,” as they are called, are suspended. Were it
not for this structure, we should not be able to bend our necks or turn
our heads.
[Illustration: OX.]
[Illustration: PIG.]
[Illustration: GOOSE.]
The accompanying illustration shows the tracheæ of three well-known
creatures. The left-hand figure is the trachea of an Ox, the central
figure that of a Pig, and the right-hand figure that of a Goose. Mr.
Tuffen West, who made the drawings, sent with them the following
remarks:--
“The tracheæ of animals furnish some very interesting examples of
variation in the form and arrangement of the rings. Their purpose,
perhaps, one can but guess at in some cases; but doubtless, as being
works of the Master Builder, careful study would be repaid.
“In the Ox the rings are very strong and close, and in form like a
horse-shoe with the ends approximated.
“In the Pig the incomplete rings are broad at one part, and narrow on
the opposite side, with a tendency to spiral arrangement. I imagine that
this would make a very rigid tube, and, indeed, it feels so in the hand.
“Then, in the Goose, the narrowed lower part is that which is figured
just before the trachea reaches the sternum. The (complete) rings are
twice as broad in one half as in the other, and by the alternate
disposition of these differing widths, a tube is formed of great
flexibility fore and aft, but almost absolutely rigid in the lateral
direction. This seems to be so marked an evidence of design as to be
calculated to greatly raise our admiration.”
[Illustration: RINGED TISSUES OF SUGAR-CANE]
[Illustration: VEGETABLE SPIRAL TISSUES TENDING TO RINGS.]
* * * * *
WE have seen several examples of ringed tissues tending to the spiral
form, and it is but natural that we should expect to find spiral tissues
tending to the ring.
In the accompanying illustration the two left-hand figures represent the
curiously modified ringed tissue which is to be found in the sugar-cane,
the left-hand figure being much more magnified than the other.
The other figures represent four examples of vegetable spiral tissues,
in which it will be seen that there is a tendency to form rings, and
that if a number of rings were substituted for the spiral, and the
object viewed in a slanting direction, it would be almost impossible to
distinguish between the ring and the spiral.
Among the most remarkable of these examples are the two right-hand
figures. That on the extreme right represents a spiral vessel taken from
the so-called root, or “rhizome,” of the Water-lily, and the other is a
similar vessel taken from a branch of the Yew-tree. It has been
suggested that to this spiral structure is due the proverbial elasticity
of the yew-tree, which has from time immemorial rendered it the best
wood for the manufacture of bows.
DIVING AND DIVERS.
It has already been mentioned that the flexible tubes used by modern
divers are constructed on the model of several structures belonging to
the animal and vegetable kingdoms.
We will now see how they are utilised.
* * * * *
IN the earlier stages of the diver’s art the Diving-bell afforded the
only means of gaining access to the bed of the sea, even in
comparatively shallow waters. The mode in which this result was obtained
was simple enough, and though it carried with it the germs of still
greater improvements, was but limited and uncertain in its action.
The reader is probably aware that if a vessel be filled with air, no
liquid can obtain admittance until a corresponding amount of air be set
free. Suppose, for example, that an empty tumbler be inserted over a
basin of very clean water, and pressed downwards, it will be found that
scarcely any water will enter it, the air having taken up all the
available space, and only allowing as much space as may be accounted for
by its faculty of compression.
It is evident, therefore, that if an enlarged tumbler could be lowered
to the bed of the sea, a man might be enclosed within it, and for a time
be able to support life by means of the air contained within the “bell,”
as this enlarged tumbler was popularly called.
It is equally evident that within a short time the air within the bell
must be exhausted, and that, unless a fresh supply could be introduced,
the diver within the bell would be as effectively drowned as if there
were no bell at all.
The accompanying illustration is a kind of chart, so to speak, of the
mode in which air was formerly supplied to the bell.
On the right hand is seen a section of the Diving-bell itself, together
with the seat on which the divers can rest. There is also an
escape-valve at the top of the bell, by which the vitiated air can pass
away; but, as it is not essential to the subject in hand, and is rather
complicated in structure, it has been omitted.
Immediately on the left of the bell is a cask, to which several heavy
weights are attached. This cask contained compressed air, and, after it
was lowered by the side of the bell, the end of the flexible tube was
taken into the bell, the tap turned, and the compressed air rushed into
the bell, taking the place of that which had been exhausted by
respiration, and was allowed to pass through the escape-valve. I may
mention that the divers unexpectedly discovered that, when they were
breathing compressed air, they could dispense with respiration for a
wonderfully long time, the amount of oxygen taken in at a single breath
being enough to renovate the blood more than could be done by several
ordinary inspirations.
[Illustration: NEST OF WATER-SPIDERS.]
[Illustration: DIVING-BELL.]
On the left hand of the illustration is seen a sketch of the nest of the
now familiar Water-spider (_Argyronetra aquatica_), taken from some
specimens in my possession.
The Water-spider is really a remarkable being. Itself a denizen of air,
breathing our earthly atmosphere just as we do, and as capable of being
drowned as ourselves, it nevertheless passes nearly the whole of its
existence under water, and in that strange locality lays its eggs and
rears its young. How this wonderful feat is performed we shall now see.
When the female Water-spider wishes to deposit her eggs, she looks out
for a suitable locality, and, being a good diver, tests the various
aquatic herbage until she has found a favourable spot, and then sets to
work on her remarkable nest, which I believe is quite original in
zoology.
After stretching a few stout threads by way of a scaffolding, she
attaches to the plant a small silken cell, shaped very much like an
acorn, but not so large. Ascending to the surface of the water, she
contrives to clasp a bubble of air between her last pair of legs, and,
laden with this airy treasure, dives below.
As soon as she has reached the entrance to the cell, which is always
below, she loosens her hold of the air-bubble. It at once rises into the
cell, and expels a proportionate amount of water. Not many of these
journeys are required before the nest is filled with air, and then the
diminutive architect spends the greater part of its time in holding on
to the mouth of the little diving-bell, and supporting life by means of
the air within it.
This nest, as the reader will see, is an exact representation of the
various diving schemes in which air-bells are the chief portions of the
machinery, although the air is conducted into them after a different
fashion.
* * * * *
WE now come to another mode of diving, in which the bell is practically
superseded by the flexible tube, which allows to the diver far more
range than can be obtained by the bell. In this case the diver wears a
peculiar dress, the chief part of which is a helmet so constructed that
air can be introduced to it from above the surface of the water, and,
after respiration, can escape by means of a valve.
Air is pumped into the tube by assistants above water, and, as the tube
is long and elastic, the diver can move about with considerable freedom.
As is the case with the diving-bell, the diver’s tube is strengthened by
an internal spiral wire, so that it is always open, however it may be
bent or twisted.
The right-hand figure of the illustration represents the diver examining
part of a sunken vessel. The tube through which he breathes is seen
passing to the surface of the water, and so is the line by which he
gives his signals to his comrades above. In his hand he holds a lamp
which can burn for a limited time, being connected by a smaller but
similarly constructed tube to a vessel of compressed air.
* * * * *
ON the left hand of the same illustration are shown the curious Rat-tail
Maggots, as they are popularly called. They are the larvæ of the common
Drone-fly (_Eristalis tenax_), which is so common towards the end of
summer, and looks so curiously like a bee.
[Illustration: RAT-TAILED MAGGOTS.]
[Illustration: DIVER WITH AIR-TUBE.]
These creatures pass their larval life buried in the mud and below the
surface of the water, and yet are obliged to breathe atmospheric air.
This they do by means of the long appendages which have gained for them
the name of Rat-tails. These “tails” are very elastic, and are capable
of elongation and contraction to a wonderful extent.
When the creature is undisturbed, it lies buried in the mud with its
head downwards, and its tail extended so that it reaches the surface of
the water. Within this tail are two air-tubes, which are connected with
the principal tracheæ, which have already been mentioned. They are
wonderfully elastic, and, when the tail is extended to its utmost limit,
are nearly straight. When, however, the tail is contracted, the tubes
become self-coiled by their own elasticity, and shrink into the base of
the tail.
As the tail is very transparent, it is easy to see how these movements
are conducted. The larvæ, which may be found in almost any stagnant
water, should be placed in a tall and narrow glass. Some mud should be
placed at the bottom of the glass, which should then be filled with
water to the depth of three inches or so.
When the mud has quite subsided, and the water become clear, the long
slender tails of the larvæ will be seen so elongated that their tips
reach just above the surface of the water. A magnifying-glass will
easily show the two tubes within the tail.
Let the glass be but slightly tapped, and all the tail is withdrawn in a
moment, so as to be out of reach of external danger. The
magnifying-glass will then show the two tubes lying contracted in the
base of the tail, and taking astonishingly little space, considering the
amount of elongation which they can sustain. And, on examining the
various bends and curves of the tubes, the value and power of the spiral
spring will at once be seen. True, they are very small, but in Nature
all things go by comparison, and our whole earth itself is as a grain of
sand upon the seashore among the grandeurs of the visible universe.
THE LEAPING SPRING.
The last of the springs which can be mentioned in this work are those
which are used for leaping purposes.
The figure on the right hand represents the common Spring-jack or
Skip-jack with which children are always so much amused. It consists of
a flattened piece of wood called the “tongue,” which is inserted into a
twisted string, so that it forms a tolerably powerful spring. When
twisted round, and then suddenly released, it strikes against the ground
with such force that the whole machine is thrown into the air.
Sometimes the Skip-jack is made of a fowl’s merrythought, as shown in
the illustration; sometimes of the breast-bone of a goose; and sometimes
of a piece of wood cut into the semblance of a frog, and painted. In all
cases, however, the machinery is practically the same. I may mention _en
passant_ that these frog Skip-jacks are most acceptable presents to
savage chiefs in many parts of the world, and that the most powerful and
venerable warriors are as delighted with these toys as any European
child of six years old.
* * * * *
NOW we will turn to Nature, and see what she has in the way of
Skip-jacks.
All entomologists will at once have before their minds the vast groups
of Skip-jack Beetles, technically termed _Elateridæ_, and also known as
Click-beetles, from the sharp clicking sound which they produce when in
the execution of their curious gymnastics. To this group belong the
fire-flies of warm countries, and it may be mentioned that the larvæ of
some of our species are too familiar to the agriculturist under the name
“wireworm.”
[Illustration: SKIP-JACK BEETLE. GRASSHOPPER.]
[Illustration: SKIP-JACK.]
All these beetles have very short legs and very long bodies, so that if
they should fall on their backs on a smooth surface, they could not
recover themselves. Now, as they, when discovered, instinctively try to
save themselves by falling to the ground, it is evident that some means
must be used to enable them to regain their position. This is found in a
most curious apparatus.
Attached to the “prothorax” is a rather long, pointed, and very elastic
projection exactly corresponding with the tongue of the Skip-jack. The
end of this tongue fits into a groove in the “sternum.”
When the beetle falls on its back, it curves its body as shown in the
illustration, the tongue thus being freed from its groove. It then
smartly springs the tongue back into its place with the sharp clicking
sound already referred to, and does so with such force that it leaps
into the air to some height.
Generally it falls on its feet, but if it should fail, it repeats the
process. If one of these beetles be laid on a plate or similar smooth
surface, it will skip ten or twelve times without stopping, and after a
short rest will begin again.
* * * * *
THERE are some curious little beings, popularly called Spring-tails,
which afford excellent examples of the Leaping Spring. Their exact place
in the system of Nature is rather uncertain, some zoologists considering
them as insects, while strict entomologists reject them. They are very
small, and mostly of a darkish brown colour.
Plenty of them may be found under stones in damp spots, under bark, and
in similar localities, though they are often found in houses, and have
frequently traversed the paper on which I have been writing this book.
Cellars are favourite localities of theirs, and a little flour sprinkled
on a plate or piece of paper in a cellar is tolerably sure to attract
them. Although they are certainly not more than the fifteenth of an inch
in length, they may be at once recognised by their peculiar attitude,
which very much resembles that of a dog or cat in its usual sitting
posture.
As long as they are not disturbed they crawl about in a quiet manner,
but if touched, or even alarmed, they suddenly make a tremendous leap,
propelling themselves by means of a forked and elastic tail, doubled
under their bodies, and acting just like the tongue of a Skip-jack.
* * * * *
BELOW the Skip-jack Beetle is shown the common Grasshopper, as an
example of muscular leaping springs.
We all know what wonderful leaps the Grasshopper, Cricket, and all their
kin can make, the leaping movement being evidently intended more as a
means of defence than as an ordinary mode of locomotion. The same may be
observed in the Kangaroos and Gerboas, which are content to use an
ordinary walking pace when undisturbed, but when alarmed can make
tremendous leaps, and outstrip almost any pursuer.
Even in Man, the Horse, the Dog, &c., which are most essentially leaping
animals, the same principle is employed, the legs being used as muscular
springs acted upon by the will of the owner.
USEFUL ARTS.