6 INTERNAL ANATOMY OF INSECTS. 
responding in number with the segments of the body, 
and sending forth nerves in pairs, the ramifications of 
which are distributed to every part of the frame. This 
may be considered more particularly with respect to its 
substance and colour ; its tunics; and parts. 
I. Substance and Colour.—The nervous apparatus of 
insects is stated by those who have examined it most nar- 
rowly, though consisting ofa cortical and medullary part, 
the latter more delicate and transparent than the former, 
to be less tender and less easy to separate than the hu- 
man brain?. It has a degree of tenacity, and does not 
break without considerable tension; in general, it is 
clammy and flabby, and under a microscope a number 
of minute grains are discoverable in it, and when left to 
dry upon glass, it appears to contain a good deal of oil, 
which does not dry with the rest>. That of the gan- 
glions differs from the substance of the rest of the spinal 
chord, in being filled with very fine aérial vessels, which 
are not discoverable in the latter®. With regard to co- 
lour, Lyonnet states that the chords of the spinal mar- 
row in the larva of the great goat-moth are of a blueish 
gray, and have some transparence?; Malpighi and Swam- 
merdam observed that the cortical part of the ganglions of 
that of the silk-worm and the hive-bee had a reddish hue, 
* Lyonnet Anatom. 100. > Ibid. 101. 
© Idid. 100. In man and the vertebrate animals, the medullary pulp 
is every where homogeneous ; under the microscope it appears to con- 
sist 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, @ Hist. 
Nat. xxii, 531—. 4 Anat. 99, 
