1815.] On ths Uses of the Dorsal Vtssel. 19\ 



Article V. 



Observations on the Uses of the Dorsal Vessel, or on the Ivjiuence 

 which the Heart exercises in the Orga?nzatio7i of articulated 

 Animals, and on the Changes luhich that Organization expC' 

 riences when the Heart or the Orga?i of Circulation ceases to 

 exist. By M. Marcel de Series. 



(Continued from Vol. iv. p. 355.) 



I BEGAN the examination of the dorsal vessel with those species 

 in which we see it beating externally. Among those I chose the 

 larvje of the coleopterae and lepidopteras. The larva of the geotrupa 

 nasicornis, being very common, seemed proper for my object. The 

 dorsal vessel of this species is elongated and cylindrical. Wlien 

 separated from the muscles and fatty membranes which surround it, 

 we see that its diameter is the same in almost the whole of its 

 length, being only a little contracted at the two extremities. Having 

 fully ascertained this disposition, I endeavoured to ascertain if there 

 were any ramifications. For this purpose I examined it with the 

 greatest attention, and with the best glasses. The contractions were 

 always confined to the dorsal vessel, and never extended beyond tiie 

 canal which runs along the back. 1 tiien placed this vessel under 

 the lens of my microscope, and' could not perceive any ramifica- 

 tions, not even in the membranes which surround it. In vain I 

 endeavoured to find some trace of them in the membrane of the 

 intestinal tube, the fibres of the muscles, especially in those of the 

 rings of the abdomen and mandibles, which ought to have presented 

 them, if any had existed, in consequence of the energy of their 

 contraction, and the need which these organs liave of vessels. 



I then examined the dorsal vessel oT the geotrupa nasicorr<^is et 

 punctata ; but all ray attention was unable to discover the least 

 ramification. I subjected to the same examination a very consider- 

 able number of coleopterie, the largest that 1 could procure, as the 

 ateuchus semi-punclatiis, cetonia aurata etfastuosa, scarites gigasy 

 cerambijx heros, blaps gi^as, and morlisciga. In all of them I 

 observed the dorsal vessel without any ramifications. These dissec- 

 tions, however, convinced me that, without a certain attention, 

 ramifications of that vessel may be supposed to exist, on account of 

 the colour and disposition of the hepatic vessels, which, being long 

 and almost capillary, spread over every part of the body, and are 

 often found fixed to it after the intestinal tube has been removed. 

 To deternjine with certainty this disposition, we must allow the 

 intestinal tube to remain, and dissect in water. This liquid lifts tip 

 the hepatic wcbicls ; so that it becomes cafcy to follow them to their 

 insertion. 



Though I could not perceive any ramifications in these species, I. 

 wiw not entitled to conclude that tlv.y did not exist iu insects. 1 



