53 ORGANIZATION AND DEVELOPMENT OF ANIMALS IN GENEEAL. 



the Invertebrata it is often possible to distinguish an anterior 

 especially widened portion of the intestine, which receives the hepatic 

 secretion and is called stomach from the posterior, narrower, and 

 longer .section, which is known as intestine. 



The hindermost section of the 

 alimentary canal or hind gut, 

 which is not always sharply 

 marked off from the intestine, 

 is especially concerned with the 

 collection and repulsion of the 

 undigested remains of the food, 

 or fpeces. It may also possess 

 csecal appendages attached to its 

 anterior part, and possessing a 

 digestive function. In the lower 

 animals it is a small structure, 

 but in the higher animals it at- 

 tains a much more considerable 

 length, and receives anteriorly 

 one (Mammalia) or two (Birds) 

 c?eca, and it may be sub-divided 

 into two pai'ts, known as large 

 intestine and rectum ; in the 

 Vertebrata its hind end receives 

 the ducts of various glands (kid- 

 ney, generative organ*, anal 

 glands). It may in addition dis- 

 charge other functions, e.g., a 

 respiratory (larvae of LibelluHdse) 

 or a secretory function (larva of 

 Ant Lion). 



The salivary glands, liver, and 

 pancreas are to be regarded as 

 outgrowths of the alimentary 

 canal which have become diffe- 

 rentiated into glands. 



The secretion of the salivary glands is poured into the buccal 

 cavity, and there performs two functions (1) it dilutes the food, 

 (2) it has a chemical action upon it, converting the starch into 

 sugar : they are absent in many aquatic animals and are especially 

 developed in herbivorous animals. 



FIG. 49. Alimentary caual of a bird. Of, 

 oesophagus; A', crop ; Din, proventriculus ; 

 A"..<, gizzard; D, small intestine; P, pan- 

 creas placed in the loop of the duodenum ; 

 //, liver; 0, the two casca; U t ureter ; Or, 

 oviduct; A<J, large intestine; Kl, cloaca. 



