352 On the Uses of the Dorsal Vessel. [Nov. 



are the smallest, while the contrary would he the case if they pro- 

 ceeded from the vessel. 



Swammerdam has described and figured the dorsal vessel of 

 insects with more accuracy than Malpighi ; but, like him, he 

 always considered it as a heart, or at least as an organ which per- 

 formed the functions of one. In giving a description of the insects 

 of his cabinet this excellent observer says expressly, " I preserve 

 eggs of the grasshopper, which are oblong, and between which 

 appear blood-vessels both veinous and arterial."* But as Swam- 

 merdam takes no further notice of this observation, except in 

 speaking of the silk-worm, f it is probable that he was misled by 

 the brownish aspect which the tracheae assumed in drying. A very 

 simple cause may have equally contributed to this illusion. The 

 inferior hepatic vessels are extremely elongated in the grasshoppers, 

 and often run along the ovarium. Hence when great attention is 

 not paid to them they may be easily mistaken for blood-vessels. 

 Swammerdam describes the dorsal vessel in his anatomical re-r 

 searches as a hollow vessel, exhibiting at intervals dilatations and 

 contractions. | He is far, however, from considering these con- 

 tractions as so many. hearts, and from believing that the liquid 

 which they contain retrogrades. He even opposes the opinion of 

 Malpighi, acknowledging, at the same time, that he does not 

 know how the bronchiae communicate with the branches of the 

 tracbeee, and these with the heart. Speaking of the larva of the 

 geotrupa nasicorna, Swammerdam observes, that along the whole 

 heart there exist moveable fibres, similar to the rings of the body. 

 These fibres, according to him, penetrate into the substance of the 

 heart itself, forming as many cords which dilate and contract it. It 

 is these moving fibres that make the dorsal vessel appear as if it 

 were composed of a series of contractions and dilatations, which 

 have deceived almost all observers. On removing them we see 

 very well, as Cuvier has observed, that this vessel is a simple tube, 

 equal through its whole length, and only smaller towards its extre- 

 mities. 



De Gcer has taken so little notice of the dorsal vessel that it is 

 difficult to know if he was sufficiently sensible of its importance. 

 His ideas can be of no weight in the question which occupies us; 

 accordingly we do not think it necessary to pay more attention to 

 them. 



As to the opinion of Lyonnet, it is very different from that of 

 those observers whom we have already mentioned. This skilful 

 anatomist does not think that the dorsal vessel of insects is entitled 

 to the name of heart, as he could never discover either veins or 

 arteries attached to it, with whatever care he made his injections 



• Biblia Naturae, t. i. p. 214. 

 t Collection Acai'emique, t. v. p. 264. 



J Hiblia Naturae, t. ii. Uh. xv. ri£. 4; t. i. p. £52 : tnb. xwiii. fifj. £•; t. i. 

 p. 31 1 ; t. ii. p. j"7 ; tab. .txxiv. fig. 6, a a ; t. ii, p. 664, tyb. xl. tij;. 4. 



