412 



PHYSIOLOGY. 



Jurine's * and Chabrier's f observations upon the structure of the 

 wings harmonise herewith ; whereas, according to Carus, there is a 

 threefold difference in the structure of the wings with respect to the 

 vessels contained within their ribs. Some, as the elytra of the beetles, 

 have blood and air-vessels ; others contain only blood-vessels ; the third, 

 lastly, as the wings of the Hymenoptera and Diptera, exhibit air- 

 vessels exclusively. But according to my opinion and observation, these 

 differences do not exist, but all the ribs contain merely tracheag or air- 

 vessels, whereas within the rib around the trachea there remains a 

 vacant space in which the juices can freely circulate, and it was in this 

 free space that Carus saw, in all those [instances where he perceived a 

 motion of the blood in the wing, the globules pass and return. 



Hence also is it that the wings derive their true significance. Oken 

 even indicated that the wings of insects were no true members, but 

 as mere continuations of the skin in which vessels were distributed, 

 they were of analogous importance to the gills, and he thence called 

 them air-gills (luftkiemen) J. But if now, as I believe it is, proved 

 that the blood actually flows through them, their function as gills is 

 placed beyond a doubt. The partial interruptions of the ribs, Jurine's 

 bullae, are the places where the blood flows immediately beneath the 

 thin membrane, and can there even imbibe oxygen from the air, which 

 is, besides, presented to it everywhere by the tracheae around which it 

 circulates. Chabrier's observation, also, that a space filled with 

 moisture is found in the under wings of the beetles , is evidence that 

 blood flows in the Avings, and such a stream can only pass through the 

 ribs contiguous to the tracheae contained within it. 



If the supposed presence of blood-vessels in certain parts of the body 

 is thus contradicted, it may likewise be inferred of the Avhole body that 

 it has no blood-vessel excepting the large dorsal vessel. Indeed 

 Joh. Miiller considers k that he has detected vessels passing from the 

 heart to the ovary ; but these connecting filaments, as we have shown 

 above, are no vessels. The proposition which I have just stated 

 is therefore proved correct to its full extent. Yet this deficiency of 

 blood-vessels in the bodies of insects is by no means so extraordinary, 

 nor is it without parallel. In the membranes also of the developing 



* Nouv. Mth. de Classer les Hymenop. Geneve, 1807. 4to. p. 48. 

 f Essai sur le Vol des Insectes. Par. 1822. 4to. p. 42. 

 : Natur. Philosophic, 2nd Ed. p. 418. No. 3337. 

 Essai sur le Vol, &c., p. 19. 



