235 
anatomy of the mole-cricket. 
two medullary cords which connect the several ganglions of 
the nervous system, are in their natural state united together 
by means of the branches of a tracheal tube which runs be- 
tween them ; a similar tube being attached to the exterior 
edge of the cords ; and the surface of what may be called 
the brain of this insect, is as beautifully characterized by the 
ramifications of the tracheae which pervade it, as the surface 
of the pia mater of the human brain by the blood vessels 
which penetrate that membrane in every direction. 
In meditating on the difficult problem of the sanguinous 
circulation of insects, it has forcibly occurred to me, that the 
tracheae may possibly be the instruments of such a circula- 
tion ; absorbing the blood or the chyle in the first instance 
from the internal surface of the alimentary canal, and thence 
conveying it to the various parts of the body ; nor is this 
opinion, however improbable it may appear, entirely gra- 
tuitous. No difficulty, I apprehend, attaches to the supposi- 
tion that such an an absorption may take place ; seeing that 
innumerable minute ramifications of the tracheae penetrate 
the intestinal canal in every part : nor does there seem any 
difficulty in admitting that the insect may, by the power of 
exhausting the air from individual tracheae, draw on the 
absorbed fluid towards those two lateral tracheal tubes, which 
are apparently a general medium of communication between 
all the other tracheae of the body. And, when once the blood 
has reached this supposed point of its course, it is manifest, 
that by whatever means the air itself is forwarded from the 
same point to the most distant parts of the body, by a modi- 
fication of the same means, the blood may be forwarded 
to the same part ; and the elegant proposition of Cuvier, 
MDCCCXXV. I i 
