170 LECTURE IV. 



and also pretty large smooth stones, which 

 serve for shell-breakers." He also says, 

 " the mullet has a stronger stomach than 

 the gillaroo trout, but that they have neither 

 the power, nor motion, nor horny lining 

 of true gizzards." 



Gizzards, like teeth, serve to subdivide 

 the food, and thereby increase the surface 

 on which the gastric fluids may act so as to 

 facilitate its solution. Though birds in 

 general have gizzards for this purpose, Mr. 

 Hunter knew, that those which feed on flesh 

 have them formed with their muscular and 

 internal coat so thin, as scarcely to be re- 

 cognizable for such organs. By feeding a 

 rook with bread, he found that the muscular 

 power of his stomach became much in- 

 creased, and its lining much thickened and 

 hardened ; a fact corresponding to many 

 other observations he had made, showing 

 that the vital powers could alter the organi- 

 zation of parts, so as to adapt them to exi- 

 gencies. 



Another mode of preparing food for so- 

 lution by the gastric fluids, is by a kind of 



