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ALIMENTARY CANAL OF FISHES. 419 



that which is in the oesophagus may be entire ; and, in specimens 

 dissected some hours after death, one may observe what Hunter 

 so well describes, ' the digesting part of the stomach itself reduced 

 to the same dissolved state as the digested part of the food.' 1 



The muscular action of a fish's stomach consists of vermicular 

 contractions, creeping slowly in continuous succession from the 

 cardia to the pylorus ; and impressing a twofold gyratory motion 

 on the contents : so that, while some portions are proceeding to 

 the pylorus, other portions are returning towards the cardia. 

 More direct constrictive and dilative movements occur, with in- 

 tervals of repose, at both the orifices, the vital contraction being 

 antagonised by pressure from within. The pylorus has the power, 

 very evidently, of controlling that pressure, and only portions of 

 completely comminuted and digested food (chyme) are permitted 

 to pass into the intestine. The cardiac orifice appears to have less 

 control over the contents of the stomach ; coarser portions of the 

 food from time to time return into the oesophagus, and are brought 

 again within the sphere of the pharyngeal jaws, and subjected to 

 their masticatory and comminuting operations. The Fishes which 

 afford the best evidence of this ruminating action are the Cy- 

 prinoids, (Carp, Tench, Bream,) caught after they have fed 

 voraciously on the ground-bait previously laid in their feeding 

 haunts to insure the angler good sport. A Carp in this predica- 

 ment, laid open, shows well and long the peristaltic movements 

 of the alimentary canal ; and the successive regurgitations of the 

 gastric contents produce actions of the pharyngeal jaws as the 

 half-bruised grains come into contact with them, and excite the 

 singular tumefaction and subsidence of the irritable palate, as 

 portions of the regurgitated food are pressed upon it. The 

 shortness and width of the oesophagus, the masticatory me- 

 chanism at its commencement, and its direct terminal con- 

 tinuation with the cardiac portion of the stomach, relate to the 

 combination of an act analogous to rumination, with the ordinary 

 processes of digestion, in all Fishes possessing those concatenated 

 and peculiar structures. Sometimes the Fishes, as, for example, 

 the Sturgeon, the Paddle-fish, the Dog-fish, and the Selache, 

 whose oesophagus is best organised to prevent regurgitation from 

 the stomach, are devoid of the pharyngeal jaws and teeth. 



Fisheirdisgbrge the shells and other indigestible parts of their 

 food : and when hooked or netted, sometimes empty their stomach 

 by an instinctive act of fear, or to facilitate escape by lightening 

 their load. 



1 xcu. p. 120. 



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