The Liverpool Standard and General Commercial Advertiser.
Liverpool, Merseyside, England, 1838-08-17 00:00:00

MECHANICS' INSTITUTION.

LECTURES ON THE STRUCTURE .4 ND HISTORY OF THE
,IRTICULdITED Rj MOLL USCO US CL.4SSES OF ../INIMALS.

On Saturday evening Dr. Grant delivered the fourth of his
highly instructive lectures, in which he explained the struc-
ture of the myriapods and true insects. The diagrams were
upon an extensive scale, and presented graphic views of the,
anatomy of the centipede, cockchafer, bee, &c.
Insects form by far the largest class in the animal kingdom,
above 150,000 different species being already known to na-
turalists, and everyday the class is receiving further additions
by the discoveries of naturalists in every quarter of the world.
These creatures inhabit every latitude and every altitude on
the face of the globe. They swarm like animalcules in the
atmosphere; in fact, they may be considered the animalcules
of the air, in like manner as the polygastric tribe are animal-
cules of the water. They swarm throughout the strata of the
earth wherever it is of a loose and porous texture, both in the
perfect state and in that of larva. They swarm even in the
water, and we observe them to employ their wings as well as
their feet to propel them through that element. They breathe
the atmospheric air by means of trachea, or air tubes, rami-
fying through every part of their bodies. Insects swarm so
much in warm climates as often to cloud the sun. The ra-
vages of the locusts are two well known in the east. Even
the ants are observed to advance in colonies resembling the
habitations of man, and they are more to be dreaded than
the lions and tigers of the forests. Insects are organized to
consume 611 forms of organic matter—animal or vegetable—
living or dead. They are the scavengers of our atmosphere,
checking the emission of the effluvia which would otherwise
arise from decayed organic substances; and thus keep the
air purified for the other tribes of organic beings. As insects
are destined to move through so light a fluid as atmospheric
air, they require a very different formation from that of the
various beings which have hitherto passed under our notice.
An insect, it is true, begins its existence as a crawling ser-
pentine worm, and is, in fact, in its adult state, but a ser-
pent flying through the atmosphere. It is not sufficient,
however, that wings should be attached to the side of a worm
to enable it to fly through the air, every part of the structure
must be contrived with a special view to the purposes of fly-
ing; for if we were to connect the wings and necessary mus-
cles to the sides of an ordinary worm and fish, the exertion
requisite to enable them to move through the air would tear
their soft and slender skeletons into pieces.

The study of insects, in consequence of the great extent of
this class of animals, forces itself upon our attention. The
ravages which they commit upon the living and dead, upon'
the vegetable and animal kingdom, are subjects which cannot
escape our observation. Insects far exceed double the num-
ber of all the vertebrated tribes of animals taken collectively.
They force themselves upon our attention by the pain which
they create, and in this we should consider that the partial
evil always tends to the general good—nature's good, of
course. Insects have likewise special charms wherewith to
engage our attention. We will not speak of the immense
supply of wax which they. alone are capable of supplying, of
the mellifluous sweets with which they delight our palates,
or of the valuable red dye which we obtain from the cochineal
insect—our business is with-their anatomy-with the means
by which an allwise Providence has enabled them to obtain
a daily subsistence and assimilate to their own likeness the
various matters upon which they feed.
The colour of insects is very beautifully adapted to the si-
tuations and circumstances in which they exist. Thus we at
once perceive that the black is the best colour for these in-
sects intended to live in dark cells, and such we find to be the
case. Who can perceive an insect in motion or at rest with-
out admiring the beauty of its proportions, its graceful ante-
nuw amid numerous eves! Look at the beautiful contrivances
by which it is enabled to walk across a roof, or the surface of
a polished mirror, without the least uncertainty, or apparent
difficulty ! Let the tempest howl and the tree shake, and see
how securely it grasps the bark in defiance of the utmost
efforts of the storm to dislodge it! Who can contemplate
the industry and patience of the ant, and not learn habits of
economy, and feel a wish to emulate its labours! Look at
the political economy of the bee, and see how well worthy it
is of adoption by the most civilised state ! We have now,
however, as we before stated, to direct our attention to that
which is not so pleasing. We have to look into the mysteries
of the organization of these beautiful beings, and investigate
the secret machinery by which they are enabled to exhibit all
those outward physical phenomena. It will at once strike
us, that as the exterior of the body of the worm is soft, it is
thereby unfitted for the adaptation of powerful wings calcu-
lated to rend the flesh asunder by their action, without the
intervention of some ossified medium fit for the action of
highly energetic muscles. We find this to be the case ; the
material of this ossified coveting is not, however, the same as
that of the muscle and lobster—carbonate of lime. That would
not answer, because it is too heavy a material, and it would re-
quire too large a mass of it mingled with animal matter to
give the required strength. Phosphate of lime, the substance of
human bones, is the chosen material, and its strength and
levity render it peculiarly adapted for the inhabitants of so
airy a region. There is a little phosphate of lime in the
corals and in the crustacea. The appearance of this exterior
skeleton is that of horn, and at one time it was taken to be
of a horny nature. But if you take a hair, and place it in
the flame of a lamp, it will dissolve and curl up. This is not
the case with the exterior covering of the beetle, as upon ig-
nition it will burn with a light flame, and still preserve its
shape. Whether the insect is in the state of a myriapod or
true insect, or arachnids, still this consolidated material
forms the exterior of the body. The body of the insect,
like that of the worm, is divided into segments, but to
a much less extent. The myriapods are a connecting
link between the worm and true insect. The myriapods
have not the same number of segments as the worm, but
they are placed at equal distances. The change from a
myriapod to an insect is still more remarkable—several seg-
ments unite and change in form. The anterior skeleton is
changed and hardened, so as to allow of the attachment of
wings, and to protect the internal organs. The myriapods
have a nervous system connected with their organs of feeling
and motion. Fortunately for animals there are many mo-
tions which go on without their cognizance. Thus man
cannot will the stoppage of the heart, of the rusts of the blood,
or of the peristaltic motion of their intestines. These go on
undisturbed whether we are asleep or awake. We can please
ourselves whether we stretch out our hand or not. The nerves
of the myriapods proceed from a great spiral cord running
through the central axis. . .

The-re are thirteen segments in the body of a true insect.
The foremost contains the organs of mastication, the mandi-
bles, and the palpi. The latter appear to be organs of sense;
but, as we have none, we cannot attempt to describe the
sensations which they produce. It would be as rational to
expect that we should be able to do so, as that a blind map
should describe blue or red. They have organs called anten-
nae, apparently connected with the sense of hearing. We
can distinctly prove the antennas to be the organs of hearing
in the crustaceous animals, but we have not been able to
satisfy ourselves on_this point with respect to insects. The
insects have compound organs of vision. There can be
counted more than 20,0(X) idcies in the eyes of an insect.
The transparent cornea can likewise be distinguished in con-
nexion with a crystalline lens. The vitreous humour has only
vet been found in aqueous insects—it exists in the leech.
The eye of the insect, however, wants the complicated appa-
ratus which we see in the higher classes of animals, such as
the eyelids, eyelashes, &c. Its place of these, the annual has
an epidermic covering over its eye which is insensible. It is
important to know how an entomologist describes an insect.
lie considers it as composed of three thoracic segments. The
first he calls the prothoracic segment, the second the mezzo
thoracic, and the third the meta. A pair of legs is attached
to each of these segments. The posterior wings are attached
to the meta thoracic segment. In flies, these are wanting,
hence they are called depterous insects. In reality there is
no such thing' as one pair of wings, but the second pair is so
small as almost to escape our notice. The forms of the wing
vary exceedingly. 'Fhey are permeated with blood vessels
and air cells, the latter of which gives them their reticulated
structure. To these three thoracic segments succeed the nine
segments of the body, which seem very like the segments of
the myriapod or worm. The last of these segments is some-
times wanting, and it is then metaphorised into the sting.
Whilst insects are in the state of larvae they are the most
voracious of animals, living seemingly but for the urpose of
enjoyment and the gratification of an insatiable ap to It
I strikes us as nothing remarkable that an insect sh d have
t
six feet. This arrangement is, however, the most remarks-
able piece of organic structure in the animal creation. That
150,000 beings, whether they have wings or no wings, should
have six feet, whether they have to have to seek their food in
dungeons, or, like the butterfly, to roam from flower to flower.
There is nothing like it in the animal kingdom. These
parts, however, are extra vascular, and they serve as means
of attachment, to allow the muscles to act. Four thousand
and sixty muscles have been counted in these organs and
connecting membranes in the body of an insect; let the
anatomist compare this with what he knows of the human
body—not one-fourth of the amount. In making the change
from a worm into an insect, an alteration takes place in all
patts of the creatures economy. 'The masticating apparatus,
the digestive organs, the nervous system, and the central
system, all undergo a change. The liver of the cockchafer
consists of a number of conglomerate tubuli ; other insects
are provided with follicular glands, for the purpose of pouring
in gastric juice to digest the food. The circulating system
of insects is a beautiful piece of mechanism. It was at one
time thought, that as the humour passes so extensively
through the body of an insect as to reach all parts of its body,
there was no necessity for a circulating system, but more
careful investigation shows- us how erroneous was this con-
clusion. We see in some insects eight segments of the heart,
each of which has a valvular structure capable of allowing
the ingress of fluid. These segments are contractable, by
which means the blood is impelled forwards. It cannot get
back, because the valves close. Every thing about this sys-
tem is as elaborately executed as in man. Who says that
insects are cold blooded? Let him place a thermometer wit hin
the hive of a bee, and he will find that it is exceedingly warm.
Through the smallness- of the creatures, and their rapid
passage through the air, there is a great loss of calaric from
their bodies; but their lungs are of the most beautiful con-
struction, and well calculated to impart a great degree of
warmth to their bodies. Let the astronomer point us out
worlds unnumbered—let him tell us of systems revolving
round centres, to an incalculable extent, in the regions of
space—until he dazzles us with the amazing extent of the
creation ; but let us not for a moment doubt that the minutest
living being is not as perfectly elaborated as the must com-
plicated system of the universe.
We are glad to find an increasing attendance of the faculty
at these lectures. This is the highest compliment which the
town is capable of paying the merits of Dr. Grant.

WHIRLWIND.—The whirlwind which we mentioned on
Wednesday as having occurred in the neighbourhood of Old-
ham on Monday evening, was felt also near Middleton, where
its violence was very great. tearing large branches from all
the trees growing in its course, and carrying them to an im-
mense height in the air. Some of them are said to have been
carried a mile from the place whence they were torn. A very
large willow tree, at Little Green Mill, near Middleton was
split up the middle during the storm; but we should rather
suppose, that this must have been done by lightning, which
was several times observed during the continuance of the phe-
nornenon.—Afanchester Guardian.

ON BATHING.—For youth of both sexes cold bathing in
summer and tepid in winter is highly useful, and ought to
be frequently indulged in; but great care is to be observed
that bathing in rivers be not commenced too early in summer,
before the water has acquired a proper degree of temperature ;
and, at all times, that there be not too great a difference be-
tween the temperature of the body and that of the water. To
expose the body to great and sudden varieties of temperature
is always dangerous. Swimming is an exercise which calls
into active exertion all the muscles of the body, and is, there-
fore, one tending much to strengthen the frame; but it ought
not to be continued for any length of time; the slightest sen-
sation of weariness should be the signal for immediately
leaving the liquid element and retreating to terra firma. To
remain in the water after this monition, is not only to throw
away all the benefits of the previous exercise, but to induce
an exhaustion of strength so great as sometimes to prove fatal.
It is truly gratifying to observe the facilities that are daily
springing up for enabling even the poor classes of society to
participate in the enjoyments of the bath; an enjoyment
which has hitherto, in our country, been regarded as a luxury,
and attainable only by the affluent, but which is, in reality, a
necessary of healthy existence, and which, therefore, ought
not to be confined to anyone class of the community. * *
* * As I have already said, bathing is highly benefi-
cial at every season of the year, and tepid bathing is perfectly
safe even in the middle of winter; if on emerging • from the
bath the body be rubbed completely dry, and active exercise
be taken no one need tear any ill consequences. It should,
however, be added, that bathing is not in every case useful;
and there are many states of the system in which it would
prove highly injurious. Delicate persons ought. therefore, to
act with great caution in this matter. I have visited most of
the baths in England, at Paris, Dieppe, and manvnther parts
of the continent, inidading that built for Napoleon at Aix la
Chapelle; but the Ladies' New Bath at Gravesend, covered
with glass, and planted with flowers and shrubs, excels them
all.—Curtis on Health.

Vtootto Entereb for totaling.

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