CHAP. XXV.] THE INTESTINAL CANAL IN VERTEBRATA. 219 



undergone a slight increase of development. The division into large and small 

 intestine, is distinct throughout the class, and often an ileo-coecal valve is pre- 

 sent. In Ophidia, the small intestine presents numerous short convolutions 

 at acute angles ; the large intestine ends in a cloaca. The intestinal canal is 

 longest in the Chelonia, and next to them in the Crocodiles. In the Chelonicij the 

 line of distinction between the large and small intestine is not so distinct as in 

 the rest, and the muscular coat is remarkable for its great thickness. The tor- 

 toises have a short, wide, and cylindrical co3cum, which is continuous without 

 interruption with the large intestine : they have also a circular ileo-co3cal valve.* 

 The great thickness of the muscular coat, and the almost total obliteration of 

 the canal during its contracted state, constitute one of the most striking pecu- 

 liarities of the intestine in Chelonian reptiles. In Batrachia, the difference 

 between large and small intestine is very distinct, being chiefly indicated by 

 difference of calibre, and in frogs a circular ileo-coecal valve ; in the toad, 

 however, there is a small ccecum, without ileo-ccecal valve. In most of the 

 Saurian reptiles, there is a ccecum according to Meckel, and generally an ileo- 

 co3cal valve : in the Crocodile the valve is present but the ccecum absent. 



In Birds, the intestinal canal, although longer than either in fishes or reptiles, 

 yet retains considerable simplicity of form. It presents much variety in length, 

 and in the number of its convolutions, according to the food and habits of the 

 bird. The duodenum, which immediately follows the gizzard, has always the 

 form of a long fold, which contains the pancreas in it. The small intestine, more 

 or less folded in different orders, terminates in a short and somewhat wide 

 large intestine, at the commencement of which are two cceca, one on each side 

 of the intestine. These cceca vary considerably in length from almost simple 

 papillseform offsets, as in the Solan goose,t to processes three feet in length, as 

 in the grouse. It sometimes occurs that there is only one ccecum. The large 

 intestine is short and straight, and is continued from the termination of the 

 small intestine, without fold, to the cloaca. There is connected with the small 

 intestine an appendage, the remains of the duct of communication between the 

 yolk-bag and the intestine in the chick. In some birds, this appendage, which is 

 said to be devoid of a muscular tunic, is as large or larger than the coeca. 



So much diversity exists in the form, length, and arrangement of the intes- 

 tinal canal in the different orders of Mammalia, that it will be necessary 

 briefly to state its peculiarities in each order. 



In Carnivora,we find examples in which the intestinal canal is remarkably 

 short in relation to the length of the body. The small intestine has but few and 

 simple convolutions ; it opens into a short ccecum (convoluted, however, in the 

 dog's) which scarcely differs in width from the rest of the large intestine. The 

 proportion in the length of the intestinal canal to that of the body, varies from, 

 according to Meckel, five to one, as in the cats and dogs ; to eight to one, and nine 

 to one, as in the hyaena and bear ; or to fifteen to one as ascertained by Meek el 

 in Phoca vitalina. The large intestine is shorter and wider than the small ; it 

 is cylindrical in form, not sacculated as in man and many others. 



In Insectivora, the intestinal canal is short, and without ccecum, the diameter 

 being pretty uniform throughout. In Sorex, according to Meckel, its length is to 

 that of the body as three to one, in the hedgehog, as six to one; in a mole, 



Meckel. f Sir E. Home's Comp. Anat. pi. civ. 



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