THE TEETH OF FISHES. 227 



body held up against these teeth, and consider the direction 

 in which the hinging of the teeth allows them to yield, it 

 will be seen that every motion tending to arrange the body 

 lengthwise, either in the median line of the mouth or in 

 either of the interspaces between the vomerine and palatine 

 bands of teeth, will meet with no obstruction, but in every 

 deviation from this position it will be caught on the points of 

 the teeth and resisted. Thus with the pike's mouth shut, 

 and the fish kept up against the palatine teeth, even its own 

 struggles will be utilised by every movement tending to 

 place it aright being allowed, and every other stopped by the 

 bands of hinged teeth entangling it. 



The structure of these teeth, and the mechanism by which 

 they are rendered elastic, have been already described 

 (page 206). 



The lingual bone, and the three median bones behind it, 

 carry small teeth arranged in oblong patches ; the internal 

 surfaces of the branchial bones (which support the gills) 

 are armed with similar small teeth ; while the last or fifth 

 branchial arch (which carries no gills, the bones forming- 

 it being called inferior pharyngeal bones,) carry larger 

 teeth. The superior pharyngeal bones (which are median 

 portions of the four anterior branchial arches) also carry 

 recurved teeth larger than those which line the rest of the 

 internal surfaces of each of the branchial arches. 



The pike's mouth and pharynx thus fairly bristle with 

 teeth, all directed somewhat backwards ; and any one who 

 has been unfortunate enough to have allowed his fingers 

 to get entangled in the mouth of a living pike will realise 

 how small a chance its living prey has of escape, when once 

 it has been seized. 



The teeth of the pike are composed of a central body of 

 osteo-dentine, on the outside of which is a layer in which 

 the dentinal tubes are directed towards the surface, as in 

 hard or unvascular dentine ; while the outermost portion of 



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