JAWS OF BIRDS. 97 



which is cloven, is turned backwards, extending into the 

 throat and acting like a valve in closing the air passage into 

 the lungs. If, when this animal has approached within a 

 certain distance of the insect it is ahout to seize, we watch 

 it with attention, we are surprised to observe the insect 

 suddenly disappear, without our being able to perceive what 

 has become of it This arises from the frog having darted 

 out its tongue upon its victim with such extreme quickness, 

 and withdrawn.it with the insect adhering to it, so rapidly, 

 that it is scarcely possible for the eye to follow it in its mo- 

 tion. The Chameleon also has a very long and slender 

 tongue, tne extremity of which is dilated into a kind of 

 club or spoon, and covered with a glutinous matter: with 

 this instrument the animal catches insects from a considera- 

 ble distance, by a similar manoeuvre to that practised by the 

 frog.* 



Serpents and Lizards have generally curved or conical 

 teeth, calculated rather for tearing and holding the food, than 

 for masticating it: like those of fishes, they are affixed partly 

 to the jaws, and partly to the palate. The Chelonian rep- 

 tiles have no teeth, their office being supplied by the sharp 

 cutting edges of the horny portion of the jaws. 



Birds as well as serpents have a moveable upper jaw; but 

 they are also provided with beaks of various forms, in which 

 we may trace an exact adaptation to the kind of food appro- 

 priated to each tribe; thus, predaceous birds, as the eagle and 

 the hawk tribe, have an exceedingly strong hooked beak, 

 for tearing and dividing the flesh of the animals on which 

 they prey; while those that feed on insects, or on grain, 

 have pointed bills, adapted to picking up minute objects. 

 Aquatic birds have generally flattened bills, by which they 

 can best select their food among the sand, the mud, or the 

 weeds at the bottom of the water; and their edges are fre- 

 quently serrated, to allow the fluid to filter through, while 



Mr. Houston has given a description of the structure of this orgjan, and 

 of the muscles by which it is moved, in a paper contained in the Transactions 

 of the Royal Irish Academy, vol. xv. p. 177. 



VOL. II. 13 



