35-i On the Uset of the Dorsal Vessel. [Not. 



dorsal vessel in one species, but says that he observed them likewise 

 in the viviparous rlv figured by Reaumur, * and also in the syrphns 

 inanL.f He goes still farther in speaking of the hee, affirming that 

 he observed in it two canals or cylindrical vessels issuing from the 

 extremity of the dorsal vessel, one of which goes to the upper part 

 of the body, and the other to the lower. These vessels furnish 

 others, all of which have vibrations more or less distinct. £ In 

 continuing his researches he speaks always of the vibrations of the 

 branches furnished by the dorsal vessel. This he does in speaking 

 of butterflies, tenebiions, and the house cricket. § Finally, when 

 he describes the dorsal vessel of the blattas, a vessel which he always 

 calls heart, he says that the blood contained in it passes into all the 

 internal parts, and that the vascular system extends to the finest 

 branches both of the external part, and of tie internal of the abdo- 

 men, thorax, head, and limbs. || 



This short statement of the observations of Comparetti proves not 

 only that this great anatomist entertained no doubts that the dorsal 

 vessel had ramifications, but that he thought he found in the insects, 

 as well as molusca, a double vascular system. It is not easy to con- 

 ceive how Comparetti was deceived in his dissections, which, though 

 delicate, are not difficult, in consequence of the small number of 

 vessels which exist in insects. To discover the cause of his error, 

 we have repeated most of his dissections with the greatest care upon 

 the very species which Comparetti points out himself. But all our 

 researches have tended to convince us that there exist no ramifica- 

 tions of the dorsal vessel of insects, nor vascular system in that 

 order of animals. This is not the case in the scorpions and spiders. 

 Accordingly these animals, which have a vascular system, present 

 as a necessary consequence circumscribed respiratory organs, in 

 place of the tracheas which we find in all the true insects. But 

 distrusting our own observations, we got them repeated by a young 

 anatomist, M. Pilar, with whose accuracy we were well acquainted. 

 Notwithstanding all the patient industry which he bestowed on this 

 subject, he was unable to discover the smallest ramification from 

 the dorsal vessel of true insects. This fact being fully ascertained, 

 we suspect that what were taken by Comparetti for vascular vessels 

 are nothing else than the inferior hepatic vessels. These vessels are 

 very long, free, and almost capillary. As they have usually a dark 

 colour, they might be easily taken for veins or arteries. This is the 

 more probable because they have often a vermiform motion. This 

 is the movement which Comparetti took for vibrations. 



Since the time of Comparetti, M. Cuvicr has established by a 

 great number of negative proofs, as well as by reasoning, that the 

 dorsal vessel in inlets has no ramifications, and that the organiza- 

 tion of these animals rendered such ramifications useless. He has 



* Tome iv. p. 11. Mrm. x. p. 181. 



t D;n;:mica Animak', Part. 1. p. 2IT, 210. 



% Ibid. p. lbi'l. p. 223, 228, 227. | Tbid. p. 230. 



