O f th e d if feren t -Orders of Muscles, b y which the
‘C a t e r p il la r is enabled to move all the various
P arts of the Bod y .
Thefe mufcles have neither the exterior form, nor the colour o f
thofe of larger animals. In their natural Hate they are foft, and
have the appearance of a je lly ; they are o f a greyilh blue, and the
Mver-coloured appearance o f the aerial or pulmonary veffels,
which creep over and penetrate their fubftance, exhibits under
the microfcope a moll beautiful fpeflacle. When the caterpillar
has been foaked for fome time in fpirit o f wine, they lofe their
e 1 aft i city and tranfparency, and become firm, opake, and white;
the aerial velfels difappear. At firft fight they might be taken for
tendons, as they are o f the fame colour, and poffefs almofl the
fame luftre. They are generally flat, and o f an equal fize
throughout; the middle feldom differs either in colour, fub-
ftance, or fize, from the extremities.
The ends are fixed to the fltm ; the reft o f the mufcle is generally
free and floating ; feveral o f them-branch out corffiderably;
the branches extend fometimes fo far, that it is not always eafy
to difcover whether they are diftin£t and Te.parate mufcles, or
parts o f another. They are of a moderate ftrength; thofe that
have been foaked in fpirit o f wine, when examined by the
miciofcope, will be found to be covered with a membrane, which
may be feparated from them, they then appear to confift of
feveral ‘parallel bands, direSed according to the length -of t’he
mufcle. Thefe, when divided by the affiftance o f very fine
needles, appear to be compofed o f ftill fmaller fafcicles o f fibres,
in.the fame diredtion, which, when examined with a very deep
magnifier.
magnifier-, and in a favourable light, appear twilled like a fmall
eord: The mufcular fibres of.the fpider, which are much larger
than thofe of the caterpillar, are found on examination to confift
of- twofubfiances, one foft, and the other hard.; the lafl is twilled
round the formerfpirally, and thus gives to it the. afore-mentioned
eord-like appearance..
I f the mufcles are feparated by. means of very fine needles, ina
drop of fome fluid, we find that they are not only compofed of.
fibres, membranes, and aerial veflels,. but alfo of. nerves; and:
from-the drops-of oil thatmay.be feen floating on the fluid, that,
they are alfo furnilhed with many un&uous particles,.
The-number-of mufcles in a caterpillar is-.very great; exceeding ;
by much thofe o f the human body ; the reader may. form fome
idea- o f their, quantity, by looking at Fig. t.anclst, 3 and 4, of
Plate XII. They, occupy the greatefl part of the head; there is
an aftonifhing number at.the oefophagus, the inteflines, &c. the
fkin is as it- were lined by different heds of them, placed one under,
the other, and ranged with very, greatifymmetry.
The-number ■ o f mufcles that our obferver has been-able t o -
diftinguifh is truly aftonifhing ; he found 1228 in the head, 1647 in .
the body, 2066 in the inteftinal tube, making in all 4041.
T he spinal marrow; and the brain of the-caterpillar, if:
they can be faid to have any, feems to have very little, relation, to
thofe of man; in the laft, the brain isinclofed in. a bony ca.vity.;:
it occupies the greatefl part o f the head, and is anfraftuous, and .-
divided .into ,lob.es.. There.is nothing fimilar to. this in the ca-ter-
' pillar^.