86 INTERNAL ANATOMY OF INSECTS. 
grub of Musca vomitaria, in which he in vain looked for 
the dorsal vessel, a fleshy part which exhibited alternate 
pulsations ; and when with a pair of scissors he made a 
lateral incision in the insect, amongst other parts that 
came out, there was one that had movements of contrac- 
tion and dilatation for several minutes,—this experiment 
was repeated with the same result upon several grubs?. 
De Geer, whose love of truth and accuracy no one will 
call in question, saw the appearance of blood-vessels in 
the leg of the larva of a Phryganea L. (as Lyonnet did in 
those of a flea); and in the transparent thigh of Orne- 
thomia avicularia he discovered a pulse like that of an 
artery’. Baker, whose only object was to record what 
he saw, speaks of the current of the blood being remark- 
ably visible in the legs of some small bugs’: what he 
meant by that term is uncertain, but they could not be 
spiders, which he had just distinguished. This author 
has likewise seen a green fluid passing through the ves- 
sels of the wings of grass-hoppers*; and M. Chabrier is 
of opinion that insects possess the power of propelling a 
fluid into the nervures of their wings and withdrawing it 
at pleasure, as they are elevated or depressed‘: but these 
two last facts must be accounted for on other principles, 
as there is clearly no circulation. 
But though these arguments, which I have stated in 
their full force, appear strong, and at first sight conclu- 
sive, those which may be urged for the more modern opi- 
nion—that no circulation exists in insects, properly so 
called,—appear to me to have by far the greatest weight. 
* Reaum. iv. 171—. > Lesser L. ii. 84. note. 
‘ De Geer ii. 505—. vi. 287. “ On the Microscope. i. 130. 
e Tid. ‘ Sur le Vol des Ins. 325—. 
