DIGESTIVE SYSTEM. 99 



extremity is inserted in a groove above the nasal apertures; by this 

 contrivance the tongue admits of being projected far out of the mouth 

 to nearly the length of the body, and thus constitutes a most efficient 

 implement for either spearing rapidly their insect food, as is the case 

 with the Woodpeckers, or, as in the Humming-bird, for probing in 

 search of nectar to the bottom of tubular flowers. 



The tongue, together with the hyoid bone that supports it, is 

 moved by- three to four pairs of muscles, which correspond to the 

 genio- stylo- and sterno-hyoid muscles in Man ; besides which 

 there is an additional pair of very short muscles. All these are 

 remarkably developed in the Woodpecker ; where we meet also 

 with a singular pair of muscles, called cerato-tracheal, which arise 

 from the trachea about half an inch beneath the superior larynx, wind 

 several times spirally around it, and are inserted into the terminal 

 portion of the hyoid cornua ; they serve chiefly to forcibly retract the 

 tongue. The most complicated condition of lingual muscles occurs 

 in the Parrots, from their being the only Birds that truly chew their 

 food. The usual number of muscles is here increased ; the most im- 

 portant being the myloglossus, which retracts and bends the tongue 

 in the direction downward. 



Organs of Touch. 



The tongue serves frequently in Birds for an organ of touch, as 

 in the Woodpeckers, where it is darted into the chinks and holes in 

 the bark of trees in search of the larvae of insects. Many Nata- 

 tores, e. g. the Ducks and Geese, and the Flamingo among the Grallae, 

 haVe the upper mandible soft and profusely supplied with nerves 

 from branches of the fifth pair, so that they possess a delicate tac- 

 tile sensibility in that part which enables them in stirring up the 

 mud with the bill in quest of food to appreciate more readily its 

 presence. An apparatus of touch is also developed at the apex of 

 the Snipe's bill, which is provided for that purpose with numerous 

 osseo-cellular depressions. 



DIGESTIVE SYSTEM. 



THE superior, inferior, and intermaxillary bones of the Bird are 

 generally invested by horny sheaths, which form in the several 

 orders and families a beak of very varied character, the modifications 

 in the structure of which are commonly depicted in Zoological works. 



