THE ORGANS OF NUTRITION. ]41 



ture in the nectar-sucking butterflies modifies this assertion. The 

 caecum might also here, as in the Mammalia, have the function of a 

 second .stomach, and thus, therefore, be more serviceable to the car- 

 nivora, which consume coarser materials than the vegetable feeders, 

 which are besides provided sometimes (Melolonthu, &c.) with ana- 

 logous organs, as the clavate and thick intestine. The caecum is repre- 

 sented in the Carabodea by the broad sack-shaped colon. The long 

 caecum of the water-beetles has, according to Leon Dufour, the func- 

 tion of a swimming bladder, which is much to be doubted in the Cole- 

 oplera, they being provided with so many air vessels : we cannot either 

 well imagine how air can be introduced into it, certainly not through 

 the anus ; for it is not for this purpose that water-beetles raise their 

 anal ends to the surface of the water, but to take air beneath their 

 elytra, as has been long well known. 



111. 



THE BILIARY VESSELS/ 



The BILIARY VESSELS (vasa billfera, (PI. XVII. XXII. K, K,) 

 occupy the first place among those organs which, although distinct, stand 

 however in direct connection with the intestinal canal. They are narrow 

 filiform tubes, which open at one end into the duodenum, and where 

 this is wanting into the ilium close behind the pylorus, and at the 

 other end are either free and closed, or pass into each other and thus 

 apparently form one vessel, which pierces the intestinal membranes 

 with both its ends. The biliary vessels also, at least according to Ram- 

 dohr, sometimes empty themselves into the end of the stomach, some- 

 times (for example, in Meloe,) upon the limits of both, that it is 

 difficult to say whether it is the stomach or intestine. According to 

 Ramdohr, the mouth of the biliary vessels does not pierce the internal 

 intestinal membrane, but only the exterior muscular one, which 

 assertion, however, is contradicted by Meckel's observation, for, by 

 pressing these vessels, he forced their contents into the intestine. In 

 fact, the biliary vessels always enter the cavity of the intestine, and 

 their mouths lie at the same height, forming a circle around it; 

 more rarely upon one side only, for example, in a vesicular disten- 

 sion of the ilium in Lygceus ap/erus. Other differences in the mode 

 of their evacuating themselves are not rare. In the flies (Muscaria') 

 the four biliary vessels unite into two short stems, which open into the 

 intestine at its opposite sides, or all four form but one, as in Cimex 



* E Salv^AU, ^ j#, t 



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