AVES. 



385 



abdominal organ. It consists of two lobes, between which anteriorly is the 

 apex of the heart, and posteriorly a double fold of peritoneum, analogous to 

 the broad ligament in the mammal. There are two hepatic ducts, one pro- 

 ceeding direct to the duodenum, the other passing from the right lobe to the 

 gall bladder, a cystic duct, proceeding from the latter to the intestine. The 

 Columbidfe or pigeon class, as also some classes of the order Scansores, have no 

 gall bladder. The vena porta, in 

 addition to its fundamental radicals, 

 is joined by branches from the femo- 

 ral and sacral veins. 



The organs of respiration in birds 

 are interesting. The nasal openings 

 are very small, and placed on each 

 side of the beak, or at its base, 

 surrounded by naked skin, a few 

 feathers, or even scales, which form 

 alfe or wings ; the nasal cavities 

 open into the pharynx by two dis- 

 tinct apertures, which lie close to- 

 gether. The air-passages consist 

 of a superior larynx, trachea, inferior 

 larynx, bronchi, bronchial tubes, 

 and air-sacs. The superior larynx 

 is situated just behind the root of 

 the tongue, opening by a longitu- 

 dinal slit. It consists of several 

 bony or cartilaginous pieces, varying 

 in number, joined by membranes 

 and moved by muscles. There is 

 no epiglottis, the sides of the rima 

 closing the orifice during the passage 

 of food. The trachea winds down 

 the neck as a single tube, composed 

 of complete bony or cartilaginous 

 rings, not overlapping, as in mam- 

 malia. They are round or com- 

 pressed, varying in diameter. The 

 syrinx, or inferior larynx, is the 

 organ of sound, and is best devel- 

 oped in song-birds, varying in form 

 and structure in different species. 

 At its origin is a membranous 

 tongue, composed of a doubling of lining membrane ; the free portion is 

 directed upwards, and its vibration produces sound. 



Below, the tube divides into a pair of bronchi, which lead to the lungs. 

 They consist of incomplete segments of bone or cartilage, completed by mem- 

 brane. The lungs are spongy, bright red, long, flat, oval, and applied against 

 the sides of the vertebra and ribs, to -which they are attached by cellular 

 tissue. They present several openings on their surfaces, which communicate 



FIG. 14;. 



Alimentary canal of a Bird, a, Inglnvies ; 6, 

 Proventriculus ; c, Pancreas ; d, Duodenum ; e, 

 Liver ; /, Biliary cyst and duct ; g, Pancreatic 

 duct ; h, Intestine ; t, The two cca ; k, Rectum ; 

 I, Right ureter ; m, Oviduct ; n, Its aperture in 

 cloaca ; o, Opening of cloaca. 



with air-sacs hollowed out in the cellular' tissue of the body. 



These sacs are 



2 c 



