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PHYSIOLOGY.

the functions just indicated. The most striking differences have alreadybeen exhibited in the remarkably divaricating form of the stomach.These divarications admit of being, as well as their functions, classedinto 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 theopening of the biliary vessels, and we therefore find

In the first case a crop, a proventriculus, and a stomach, but whichwe shall call henceforth the duodenum, as it corresponds in functionwith that organ of the higher animals. In a thus formed intestine thehardest animal and vegetable substances are digested.

In the second case, in which the proventriculus is wanting, the cropand duodenum are united in a single narrow and equally wide tube,which may be here properly called the stomach. We find this stomachin* all insects which feed upon light vegetable, or even corrupt pappyanimal substances. Sometimes this entire stomach, like the duodenumof the carnivora, is throughout shaggy.

In the third case a true proventriculus is indeed wanting, but wesometimes observe an analogous form. These are wholly deficient inthe Lepidoptera ; 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 andduodenum, but the crop is wanting. The same is the case in theDiptera . but the stomach, together with that portion of the intestineforming the duodenum, is very long, round, and tubular. The Hymeno-ptera have a wide crop, which serves as a sucking stomach, a funnel-shaped orifice to the stomach, which represents the proventriculus, anda tolerably long transversely ridged duodenum. The Hemiptera ,lastly, exhibit again all three divisions, but in these they are morewidely separated: the crop is the first broad, purse-shaped stomach;the proventriculus we again find as a thin but compact muscular tubularsecond stomach; the duodenum is thus in the Cicadaria the narrow,but in the bugs wider, transversely ridged, third stomach, which isfurnished with auxiliary ducts. If but two stomachs are present the