380 



BILL AND TONGUE OF BIRDS. 



FIG. 198. BEAK OF HORNBILL. 



(Fig. 197). A still more remarkable modification of this organ 

 is presented by the Pelicans (Fig. 303), aquatic Birds, that carry 

 between the two branches of the lower jaw a large and very 



extensible pouch of 

 skin ; in which they 

 store up the produce 

 of their fishing, after- 

 wards disgorging it, 

 and feeding on it at 

 their leisure. We 

 must also remark that 

 the beaks of some 

 Birds present singu- 

 larities of form, the 

 use of which is not known to us; such, for instance, as the 

 kind of helmet on the top of the bill of the Cassowary 

 (Fig. 276) ; and a similar excrescence on the beak of the 

 Hornbill (Fig. 198). 



843. The tongue is sometimes employed in the prehension 

 of food, as well as in deglutition; and presents remarkable 

 peculiarities of structure. The Os Hyoides, on which it rests, 

 is prolonged backwards in the form of two horns, which rise 

 behind the head, and which give attachment at their extremity 

 to muscles (m Fig. 199) fixed anteriorly to the lower jaw; 

 when these muscles contract, they draw these horns downwards 

 and forwards, and conse- tr a v m h t 



quently push the tongue out 

 of the mouth. This mecha- 

 nism is particularly curious 

 in the Woodpeckers, and in 

 other Birds which dart out 

 their tongues with rapidity Fro 199 ._ ToNGUE> GLOTm> &c . . ,, tongue; 



On the insects which COnsti- , hyoid bone; m, muscles; p, pharynx; g, 

 i f j /TT ctf\f\\ glottis ; tr, trachea ; e, oesophagus. 



tute their food (Fig. 200). 



This organ also presents important differences in its form. 

 In the Parrots, which to a certain extent masticate their food, 

 the tongue is thick and fleshy ; in Birds of Prey it is broad and 



