THE ORGANS OF NUTRITION. 123 



fore make a primary separation of it into its SEVERAL DIVISIONS and 



its APPENDAGES. 



The divisions of the intestinal canal are, the PHARYNX, the (ESO- 

 PHAGUS, the CRAW, the PROVENTRICULUS, the STOMACH or VENTRI- 

 CULUS, the DUODENUM, the ILIUM, the CCECUM, and the COLON. 



The peculiar appendages of the intestinal canal are, the SALIVARY, 



BILIARY, and ANAL VESSELS. 



These parts are never all present together ; sometimes one is wanting, 

 and sometimes the other. For example : insects with a suctorial mouth 

 never possess apparent pharynx, but the oesophagus originates imme- 

 diately at the base of the sucking tube ; they also want the proven- 

 triculus, instead of which they possess a bladdered crop, which how- 

 ever does not occur in mandibulated insects. The part most frequently 

 deficient is the duodenum, which has hitherto been observed only in 

 some of the pentamerous Coleoptera, after which the ccecum is least 

 frequently present, for it appears to be peculiar to those families only 

 the genera of which feed upon animal matter. 



With respect to the appendages, the biliary vessels are seldom want- 

 ing (Chermes, Aphis}, the salivary ones frequently, but the anal vessels 

 very generally. 



THE PHARYNX. 



101. 



The pharynx is the distended commencement of the oesophagus, 

 bordering upon the cavity of the mouth, and is found, as we have 

 recently remarked, only in the mandibulata, consequently in the Cole- 

 optera, Orthoptera, Neuroptcra, and Hymenoptera. In these it is 

 nothing else than the almost trumpet-shaped commencement of the 

 oesophagus, and in the majority of cases is not separated from it by any 

 evident difference of texture or construction. In some of the grass- 

 hoppers and cockroaches, in which, in consequence of their large man- 

 dibles, the cavity ' t of their mouth is very expansive, their pharynx is very 

 much distended, and more clearly separated from the much narrower 

 oesophagus *. Its membrane is more dense and compact than that of 

 the latter, excepting which it displays no other difference. The mucous 

 and muscular membranes lie close together, and it is scarcely possible to 



* Ramdola, ib. PI. I. f. ( J. 



