INTRODUCTION. xv 



bruising throat teeth work, and thus whatever food^which in the Cyprinidce is frequently of a 

 vegetable nature — passes into the oesophagus undergoes a triturating process whereby it is 

 more readily rendered digestible. 



The stomach of a fish is usually of a large size; it varies, however, both in size and 

 shape ; generally it forms a curved tube, like a siphon ; the descending portion is called 

 the cai-dia, the ascending part is the pylorus, which is generally provided with a valve. 

 Sometimes the pyloric portion has its walls very much thickened, as in the Salmo stomacliicus, 

 or Gillaroo* Trout of the lakes of Ireland. Behind the pyloric opening of the stomach there 

 are in many fish a number of blind tubes called the appendices pylorica, or "pyloric caeca;" 

 they vary in number as well as in structure ; there may be only two or three of these 

 caeca, or there may be as many as two hundred; in form they may be simple short tubes, 

 sometimes mere cylindrical capsules, as in Cole's Charr {Salmo colii), or they may consist of 

 elaborate branches. It is supposed these appendages perform the function of the pancreas; 

 in many fish they are altogether absent. Attention should always be given to these pyloric 

 caca, as they are sometimes of value in determining a species ; the Galway Sea Trout {Salmo 

 gallivensis), for instance, is at once recognised from the Common Sea or Salmon Trout (5. 

 trutta) by the excessive shortness of these blind tubes. 



Some fish are entirely carnivorous in their habits, others are to a great extent herbivorous ; 

 the solvent power in a voracious species of fish is most conspicuously exemplified; if, for in- 

 stance, a Pike be captured soon after it has swallowed its prey, the head portion of the same, 

 which is the part that generally first reaches the stomach, will be found more or less digested 

 and dissolved, whilst that part which still remains in the gullet may remain entire. It is 

 mentioned by Aristotle and other ancient writers as a curious fact, that the only fish known 

 to ruminate is the Scarus.f 



It appears, however, that amongst the Cyprinida:, as the Carp, Tench, Roach, &c., and 

 other herbivorous fishes, rumination is quite a normal process, and here the curious throat- 

 teeth play a most important part. "The muscular action of a fish's stomach," says Professor 

 Owen, "consists of vermicular contractions, creeping slowly in continuous succession from the 

 cardia to the pylorus, and impressing a two-fold 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 intervals of repose, at 

 both the orifices, the vital contraction being antagonized 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 mophagus, 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 Cyprinoids (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 predicament, laid open, shows well 



* The name of Gillaroo is a corruption of the Irish words gilla, gilk, "a boy," "an attendant," and ruadh, 

 "red;" "the red fellow," in allusion to the bright large red spots on this fish. Gill is the root of the word "gillie," 

 the Salmon Fisher's gillie or attendant. Compare the Anglo-Sa.xon gilda, "a companion." 



t The Scarus of the Ancients is doubtless the Scariis cretcnsis of Aldrovandi, a Mediterranean species noticed 

 by Spratt and Forbes, still abundant on the Lycian shores ; by means of its parrot-shaped mouth, it bites off and 

 feeds on the stony corallines, nullipores, &c., its chief food. It is probable that the Scarus returns portions oj the 

 hard coralline contents of the stomach for trituration. Oppian has most clearly expressed the ruminating process in 

 this fish in the following words — 



Kal fJ.OVl'O'i tOTjTVV 



ai.ynppov TTpoitjo'i'.i' ava, arofj-a. diurepoi' auri-: 

 BaMuuei'dii, iA,ri\.oio-iv avaiTTViTcrwv laa (poa/Brju. 



(Hal. i. 2.) 



