86 INTERNAL ANATOMY OF INSECTS. 
travascular, or without peculiar vessels analogous to veins 
and arteries. 
I shall now enlarge a little upon each of these hypo- 
theses, beginning with the first or original one. 
No one will deny that the argument from analogy is 
strongly in favour of this : I need not therefore dwell 
upon it, but proceed to others. Swammerdam, to whose 
exactness in observing, and scrupulous accuracy, every 
reader of his immortal work will bear testimony, ex- 
pressly asserts that he has seen vessels issuing from the 
dorsal vessel in the silkworm, and even succeeded in 
injecting them with a coloured fluid a . Now it seems 
extremely improbable that so practised and expert an 
anatomist should have been deceived, especially upon a 
point which would naturally excite his most earnest and 
undivided attention. Without this recorded experiment, 
perhaps, it might be thought, though' this was very un- 
likely, that he had mistaken bronchia for veins and ar- 
teries : but how could they have been injected from the 
supposed heart? Another great physiologist, Reaumur, 
in the caterpillar of the saw-fly of the rose (Hylotoma 
Rosiv) observed, besides the dorsal vessel, a ventral one 
of similar form, in which also was a pulsation, but slower 
than that of the other. This he supposes may be the 
principal trunk of the veins b . Bonnet thought he dis- 
covered a similar vessel in a large caterpillar, but with 
a His words are — "In silkworms I have clearly seen various small 
vessels spring from and approaching to the heart, which I have even 
filled with a coloured liquid. But whether they were veins or ar- 
teries I cannot yet affirm." i. 112. a. 17(5. a. According to Cuvier 
(Anat. Com p. iv. 418), but I cannot find the passage, Swammerdam 
als<5 mentions having seen a red fluid issue from small vessels in grass- 
hoppers. ' Reaum. v. 103. 
