INTERNAL ANATOMY OF INSECTS. 7 
chord, in being filled with very fine aerial vessels, which 
are not discoverable in the latter \ With regard to co- 
lour, Lyonet states that the chords of the spinal mar- 
row in the larva of the great goat-moth are of a blue- 
ish gray, and have some transparence 13 ; Malpighi and 
Swammerdam observed that the cortical part of the gan- 
glions of that of the silk-worm and the hive-bee had a red- 
dish hue, while the medullary part was white c ; Cuvier 
relates that the brain and the third ganglion in Hypo- 
gymna dispar, with us a scarce moth, differed in colour 
from all the rest, being quite white, while the others 
were more or less tinted, and examined under a lens ap- 
peared variegated by reddish sinuous markings, resem- 
bling blood vessels as they are seen in injected glands d . 
II. Tunics. — The coats that inclose the various branches 
of the nervous system in insects seem analogous to those 
of vertebrate animals. The first thing that strikes the 
eye, when these parts in a recent subject are submitted 
to a microscope, is a tissue of very delicate vessels, which 
ramify beyond the reach of the assisted sight; these are 
merely air-vessels or bronchia derived originally from 
the trachea; of the animal : but besides these is an ex- 
terior and an interior tunic ; the first corresponding with 
the dura mater of anatomists ; and the other, which is 
a Lyonet Anatom. 100. In man and the vertebrate animals, the 
medullar} pulp is every where homogeneous ; under the microscope 
it appears to consist of a number of minute conglomerated globules. 
M. Vauquelin has analysed it, and found it to contain, of water 80 
parts; of albumen in a state of demicoagulation 7*0; of phosphorus 
1*50; of osmazone 1*12; of a white and transparent oily matter 
4 - 53; of a similar red do. 0"75 ; of a little sulphur and some salts 
5-15. N.Dict. d'Hist. Nat. xxii. 531—. >> Anat. 99. 
c Malpigh. de Bombye. 20. Swamm. Bill. Nat. i. 224. a. 
d Anat. Comp. ii. 348. 
