Supplement to the fourth, fifth and sixth editions of the Encyclopaedia Britannica > Volume 5

lagenhousz
II
Insec ta.
I N G
10. Nouvelles Experiences et Observations, 2 vols.
8vo. Paris. On different' subjects of natural philo¬
sophy. In German by Molitor, Vermischtc Schrif-
ten. Vienna, 1784.
11. On the Influence of the Vegetable Kingdom in
the Animal Creation. Phil. Trans. 1782, p. 426.
Asserting the accuracy of his experiments, and de-
nying some statements of Dr Priestley ; advancing, in
particular, many arguments to prove that the air ob¬
tained is really supplied by the vegetables, and not
by the water in which they are usually immersed, in
order to collect it. Dr Ingenhousz was, on all oc¬
casions, anxious to support his claim to this very in¬
teresting discovery; and he insisted that Priestley’s
earlier experiments, on the green matter contained
in stagnant water, had little or nothing in common
with his own, because that matter was, in fact, of an
animal nature. He was in the habit of collecting the
INS
41
Insecta.
gas from cabbage leaves, and of keeping it bottled Ingenhousz
up in his pocket; and he was prepared with some
coils of iron wire fastened into the corks, in order to
exhibit the brilliant phenomenon of their combus¬
tion to his friends : the public being at that time less
accustomed to this dazzling exhibition, than it has
become in later years, when elementary lectures on
chemistry have been more commonly addressed to
mixed audiences than heretofore.
12. Essay on the Food of Plants, 8vo. Lond. 1798.
From the French.
13. Dr Ingenhousz also inserted some essays in dif¬
ferent volumes of the Journal de Physique ; but they
possess less originality and importance than his Eng¬
lish publications.
(Chalmers’s Biographical Dictionary, XIX. 8vo.
Lond. 1815—Kesteloot, in Biographic UniverseUe,
XXL 8vo. Paris, 1818.) * (u. N.)
INSECTA
1 he animals which Linnaeus included in his class
Insecta have been distributed into four classes by
modern naturalists. These are termed, Crustacea,
Myriapoda, Arachnides, and Insecta. The dis¬
tinguishing character of these different groups have
already been laid before our readers under the arti¬
cle Annulosa, in which the systematical divisions
of the three first have been pretty fully illustrated.
In regard to insects, a reference was there made to
the present article. In the fulfilment of our plan,
we shall now take a view of the structure and phy¬
siology of insects; their classification, and the me¬
thods of preserving them for the cabinet, which are
now in use.
I he attention of naturalists, in general, has been
confined to an examination of the forms of insects
and the number of their parts. Their internal struc¬
ture has been in a great measure overlooked, and
little accurate information is known concerning
many of their functions. The task, indeed, of exa¬
mining the anatomy of insects is one of peculiar
difficulty. The organs, in many cases, are compli¬
cated in their structure, and limited in size, so that
in dissecting them, the point of a needle must fre¬
quently be employed instead of a scalpel, and the
eye requires the assistance of high magnifiers. There
are few, therefore, who have prosecuted this de¬
partment of the subject with zeal or success, and
who have inspired others with confidence in the ac¬
curacy of their statements. Swammerdam and
Ljmnet, however, form illustrious exceptions.
’Ian of this In the observations which we propose to lay be¬
n-tide. fore our readers in this article, we will confine our¬
selves, in the first place, to a brief exposition of the
anatomy and physiology of insects, as the statements
are given in considerable detail in the Encyclopcedia,
under the article Entomology. It was necessary,
however, to advert again to the same subject, for the
purpose of noticing some of the recent discoveries
which have been made by modern naturalists. In
VOL. v. part 1.
the second part of the article, there will be given an
abridged view of the modern method of classifying
insects. In the illustration of the first part of the
subject, we shall begin by considering,
I—The Organs of Protection and Motion.
The skin of insects serves the double purpose of
protection and support, and represents the cutane¬
ous and osseous systems of the vertebral animals.
Its structure appears much more simple than in the
higher classes, as it can neither be said to possess a
mucous or cellular web or true skin. It bears the
nearest resemblance to the cuticle of the skin of the
higher classes, or rather, all the laminae of perfect
skins are here incorporated into one uniform plate.
It exhibits very remarkable varieties of texture. In
some insects, as the house-fly, it is soft and pliable,
while in others, as some of the weevils, it approaches
the consistence of bone. In some species it is elas¬
tic, in others brittle.
The appendices of the skin consist of spines, hairs,
and scales. The spines are merely projecting por¬
tions of its substance, and are usually distributed
over certain parts of the feet, to aid the locomotive
powers. Hairs are often distributed over the whole
body; and, while they pass into spines on the one
hand, they become, on the other, so exceedingly
fine as to require the aid of a powerful magnifier to
trace their character. These spines and hairs, being
merely elongations-of the skin, are not easily rubbed
off. It is otherwise with scales. Some of these are
inserted into their skin at their proximal, and are
free at their distal extremity, and are so feebly con¬
nected, as to fall olf, in many species, by touching:
them with the finger. These scales, in the butterfly,
bear a remote resemblance to feathers in their form,
and are very extensively used as pleasing objects for
the microscope.
The Muscles ol insects appear to possess the
same internal structure as the same organs in the
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