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 1 . 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 

 Rosa) 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 



n 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. 176. a. According to Cuvier 

 (Anat. Comp. iv. 418), but I cannot find the passage, Swammerdam 

 also mentions having seen a red fluid issue from small vessels in grass- 

 Jioppers. b Reaum. v. 103. 



