184 THE VITAL FUNCTIONS. 



with a hard cuticle, as in birds, but also with 

 numerous rows of teeth, of various forms, answering 

 most effectually the purpose of dividing, or grinding 

 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 di- 

 gestion, which constitutes the true stomach.* In 

 the lower part of this organ a peculiar fluid secre- 

 tion is often intermixed 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 filaments : and which float loosely in the general 

 cavity of the body, attached only at their termina- 

 tion, where they open into the alimentary canal. t 

 In some insects these tubes are of larger diameter 

 than in others ; and in many of the Orthoptera, as 



* It is often difficult to distinguish the portions of the canal, 

 which correspond in their functions to the stomach, and to the first 

 division of the intestines, or duodenum ; so that different naturalists, 

 according to the views they have taken of the peculiar office of these 

 parts, have applied to the same cavity the terra oi' chyliferous sto- 

 mach, or of duodenum. See the memoir of Leon Dufour, in the 

 Annales des Sciences Naturelles, ii. 473. 



t The first trace of a secreting structure, corresponding to hepatic 

 vessels, is met with in the Asterias, where a double row of vesicles 

 ore attached to the caecal stomachs of those animals, discharging 

 their fluid into these cavities. The flocculent tissue which sur- 

 rounds the intestine of the Holothvria, is probably also an hepatic 

 apparatus : and the same observation applies generally to the Anne- 

 lida, in which neither a liver, nor hepatic vessels have been distinctly 

 traced. 



