3U2 PHYSIOLOGY. 



the functions just indicated. The most striking differences have already 

 been exhibited in the remarkably divaricating form of the stomach. 

 These divarications admit of being, as well as their functions, classed 

 into the following three chief heads : 



A. The digestion of FIRM, partly animal, partly vegetable sub- 



stances. These take place, 



a. By the aid of a crop, 



b. Without a crop. 



B. The digestion of LIQUID substances always takes place with- 



out the assistance of a crop. 



The form of the intestinal canal is thence adapted as far as the 

 opening of the biliary vessels; and we therefore find 



In the FIRST case a crop, a proventriculus, and a stomach, but which 

 we shall call henceforth the duodenum, as it corresponds in function 

 with that organ of the higher animals. In a thus formed intestine the 

 hardest animal and vegetable substances are digested. 



In the SECOND case, in which the proventriculus is wanting, the crop 

 and duodenum are united in a single narrow and equally wide tube, 

 which may be here properly called the stomach. We find this stomach 

 in all insects which feed upon light vegetable, or even corrupt pappy 

 animal substances. Sometimes this entire stomach, like the duodenum 

 of the carnivora, is throughout shaggy. 



In the THIRD case a true proventriculus is indeed wanting, but we 

 sometimes observe an analogous form. These are wholly deficient in 

 the Lcpidoptera ; their small oval food bag is both stomach and duo- 

 denum, and the crop is changed into the sucking bladder. In cater- 

 pillars the long, broad, cylindrical stomach is likewise stomach and 

 duodenum, but the crop is wanting. The same is the case in the 

 Diptera, but the stomach, together with that portion of the intestine 

 forming the duodenum, is very long, round, and tubular. The Hymeno- 

 plera have a wide crop, which serves as a sucking stomach, a funnel- 

 shaped orifice to the stomach, which represents the proventriculus, and 

 a tolerably long transversely ridged duodenum. The Hemiplera, 

 lastly, exhibit again all three divisions, but in these they are more 

 widely separated : the crop is the first broad, purse-shaped stomach ; 

 the proventriculus we again find as a thin but compact muscular tubular 

 second stomach ; the duodenum is thus in the Cicadaria the narrow, 

 but in the bugs wider, transversely ridged, third stomach, which is 

 furnished with auxiliary ducts. If but two stomachs are present the 



