82 



COMPARATIVE ZOOLOGY. 



Fishes to disgorge the indigestible parts of their food, and 

 some, as the Carp, send the food back to the pharynx to 

 be masticated. The stomach is usually bent, like a si- 

 phon; but the intestine is nearly straight, and without 

 any marked distinction into small and large. Its append- 

 ages are a large liver and a rudimentary pancreas. 



In the Amphibians, as the Frogs, the digestive appara- 

 tus is very similar to that of Fishes; but the two kinds 

 of intestines can be more readily 

 distinguished. The Reptiles gen- 

 erally have a long, wide gullet, 

 which passes insensibly into the 

 stomach, and a short intestine 

 (about twice the length of the 

 body) very distinctly divided into 

 small and large by a constric- 

 tion. 43 The vegetable -feed ing 

 Tortoises have a comparatively 

 long intestinal tube ; and the 

 Serpents have a slender stomach, 

 but little wider than the rest of 

 IO. 47. Aimt.miy of a Cepimiopod the alimentary canal. 



(diagram): a, tentacles; b, masti- m . . - . ~ ... 



calory apparatus; c, eye; d, sali- Ihe Stomach OI the (JrOCOdllC 



?Z$^?J^J^& is more complex than any liitli- 



Ifc resembles 



Ink-bag; , ovary; p, oviduct; p, that of the Cuttle-fish, l)llt offei'S 

 liver ; r, gill contained in the hrnn- ... ., . 



chial chamber; , branchial heart; a Still mOl'6 Striking analogy to 



Systemic heart 5 * mantle. the ^^ Q{ ft ^ having 



very thick walls, and the muscular fibres radiating pre- 

 cisely in the same manner, so that, in this respect, the 

 Crocodile may be considered the connecting link between 

 Reptiles and Birds." In Crocodiles also the duodenum, 

 with which the intestine begins, is first distinctly defined. 

 Into this part of the intestine the liver and pancreas, or 

 sweet-bread, pour their secretions. Furthermore, in the 



