CHYLIFICATION. 151 



trituration, furnished, not merely with a hard cuticle, as in 

 birds, but also with numerous rows of teeth, of various forms, 

 answering most effectually the purjDOse of dividing, or grind- 

 ing into the minutest fragments, all the harder parts of the 

 food, and thus supplying any deficiency of power in the jaws 

 for accomplishing the same object. Thence the aliment, 

 properly prepared, passes into the cavity appropriated for 

 its dio-estion, which constitutes the true stomach.* In the 

 lower part of this organ a peculiar fluid secretion is often in- 

 termixed with it, which has been supposed to be analogous 

 to the bile of the higher animals. It is prepared by the 

 coats of slender tubes, termed hepatic vessels, which are 

 often of great length, and sometimes branched or tufted, or 

 beset, like the fibres of a feather, with lateral rows of fila- 

 ments, and which float loosely in the general cavity of the 

 body, attached only at their termination, where tliey open 

 into the alimentary canal. t In some insects, these tubes are 

 of larger diameter than in others: and in many of the or- 

 thoptera, as we shall presently see, they open into large re- 

 ceptacles, sometimes more capacious than the stomach itself, 

 which have been supposed to serve the purpose of reservoirs 

 of the biliary secretion, pouring it into the stomach on those 

 occasions only when it is particularly wanted for the com- 

 pletion of the digestive process. J 



* It is often diflficult to distinguish the portions of the canal, which cor- 

 respond in their functions to the stomach, and to the first division of the in- 

 testines, or duodenum; so that different naturalists, according to the views 

 they take of the peculiar office of tliese parts, have applied to the same ca- 

 vity the term of chjllferous stomach, or of du'odmum. See the memoir of 

 Leon IJufour, in the Annales des Sciences Naturelles, ii. 473. 



f The first trace of a secreting structure, corresponding to hepatic vessels, 

 is met with in the Asierlas, where the double row of minute lobes attached 

 to the cxcal stomachs of those animals, and discharging their fluid into these 

 cavities, are considered by Cams, as performing a similar office. The floc- 

 culent tissue which surrounds the intestine of the Ilolothuria, is probably, 

 also, an hepatic apparatus. 



\ A doubt is suggested, by Lcon Dufour, whether the liquid found in 

 these pouches is real bile, or merely aUmcnt in the progress of assimilation, 

 Ann. Sc. Nat. ii. 478. 



