THE EESPIEATOET SYSTEM. 2 1 5 



muscles. They speak with the aid of their tongue and beak 

 alone. The syrinx may be altogether absent, as in the American 

 Vultures and in the Ostrich and its allies. 



The lunys are two oval flattened organs fixed in and imbedded 

 between the ribs from the second dorsal vertebra to the kidneys. 

 Their texture is loose and spongy. The two ^ronehi penetrate 

 their anterior surface, and divide into four or six branches ter- 

 iiiina.ting by side openings on the surface, which openings com- 

 municate with air-sacs, which are usually nine in number. 



Fig. 166. 



Diagram of a Lobclh op the Lung op a Eird : greatly magnified 

 (flfter Thomas Williams). 



Normally one of these is situated between the clavicles, and 

 gives out a process on either side which, passing into the axilla 

 or " arm-pit," enters the humerus *. Two others penetrate 

 the abdomen, and often enter the sacral vertebrae and each 

 femur ; four permeate the more anterior region of the trunk, 

 and two go to the neck. The latter often send branches into 

 the bodies of the cervical vertebrae. These air-sacs do not 

 supply air to the cranial bones. These are supplied from the 

 nose and the cavity of the outer part of the ear. 



* John Hunter tied the windpipe of a fowl and then divided the humerUs, 

 and he found that it breathed through the aperture in that: bone. 



