190 



INTEODUCTORY CHAPTER. 



size. Tlie Crane, Grus cinerea (Fig. 64), lias the bill rather 

 longer than the head, strong, straight, compressed, and pointed at 

 the extremity ; the sides of the mandible deeply channelled with 

 nostrils, and closed backwards by a thin membrane. 



Fig. 64. 



In the Goose, genus Anser (Fig. 65), we find the bill short, 

 not longer than the head, conical, covered at the base with a cerous 

 skin, with under mandible smaller than the upper. In the Spar- 



rows, Passerina (Fig. 66), the bill is strong and conical, the 

 upper mandible slightly curved, the lower compressed and smaller 

 than the upper ; nostrils lateral, basal, round, and partly con- 



Fig. 66. 



Fig. 67. 



cealed by the short feathers at the base of the mandibles. In 

 the Goatsuckers, Caprimulgus (Fig. 67), the bill is remarkably 

 small and weak, the sides inflexed and sometimes gaping. 



The tongue, like the bill, however, is only an accessor jr to the 

 digestive apparatus ; for while the beak serves the purpose of 

 prehension and trituration, the tongue assists in deglutition or 

 swallowing. Digestion is so active in some birds, that thev "•et 

 fat in an excessively short space of time. The Ortolan Bunting, 

 Eriiheriza hortidana, and some others, are fattened for the table in 



