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COMPARATIVE ANATOMY 



vi- 



pharynx and stomach. The former is a fun- 

 nel-shaped enlargement at the cephalic end 

 with several pairs of lateral diverticula called 

 the pharyngeal pouches. These pouches in 

 some animals break through to the outside of 

 the body to form slits (Fig. 295). The 

 stomach may be of many shapes and sizes in 

 the various animals. That portion of the 

 stomach that meets with the oesophagus (the 

 narrow tube connecting pharynx and stomach) 

 is known as the cardiac portion, while the cau- 

 dal opening of the stomach is called the py- 

 lorus (Fig. 438). It will be found that this 

 pyloric end is rather thick and tough. There 

 is a valve here which closes so that the stom- 

 ach can be converted into a closed sac. A 

 rather thick short portion of the intestine im- 

 mediately-caudal to the pylorus is known as the 

 duodenum. Then follows the small intestine, 

 varying in length in all the animals, which ends 

 in the large intestine, and this in turn connects 

 directly with the anal opening to the exterior 

 of the body or in a terminal enlargement 

 which quite often receives the openings of the 

 urinary and reproductive systems before con- 

 necting with the anal opening. In such cases 

 as the latter the thickened portion of the large 

 intestine is called the cloacal chamber, or sim- 

 ply the cloaca. (Fig. 426, III.) 



In fishes, amphibians, and sauropsida, the 

 cloaca is an important structure. In none of 

 the mammals except the montremes does it ap- 

 pear as a distinct organ. 

 There are various important diverticula of various shapes thrown 

 out along the digestive tract. The lateral pharyngeal pouches have al- 

 ready been mentioned. In fishes one often finds quite numerous pyloric 

 caeca. In mammals at the beginning of the large intestine where the 

 small one enters it there are colic caeca. In man as well as in several 

 other forms of mammals one of these little blind sacs is called the appen- 

 dix vermif ormis. . In birds one finds cloacal caeca. 



DETAIL STUDY 



The pharynx is that open portion behind the nose and mouth in 

 mammals which extends down to the voice box. From there downward 

 (including the voice box) the open portion is called the larynx. 



Fig. 428. 



Reconstruction of the diges- 

 tive canal of man. al, allantoic 

 stalk ; cl, cloaca ; g, glottis ; h, 

 hyoici arch ; li, liver ; lu, lung ; 

 md, mx, mandibular and maxil- 

 lary arches ; n, nasal pit ; o, 

 omphalomesenteric vein ; , 

 stomach ; v, visceral arches ; vi, 

 vitelline stalk ; w, Wolffian body. 

 (From Kingsley after His). 



