STRUCTURE OF BIRDS. 61 



several of these differences in treating of the birds whose his- 

 tory I propose to sketch. It will in the meantime be useftil 

 to give a short account of the form of intestinal canal presented 

 by a family very closely allied to that of which the Preregrine 

 Falcon is a member. 



Plate V. represents the digestive organs of a Male Sno^^'y 

 Owl, Sf/mia Nyctea. Fig. 1. is a front view of the oesophagus, 

 trachea, heart, liver, and part of the body. Fig. 2. shews the 

 lower part of the oesophagus, the stomach and the intestines, 

 which were concealed by the parts shewn in Fig. 1. Fig. 3, 

 the tongue and glottis ; 4, part of the inner surface of the pro- 

 ventriculus ; 5, a transverse section of the proventriculus; 6, 

 four of its glandules enlarged ; 7, the inner surface of the sto- 

 mach ; 8, the rectum, cloaca, and coeca. 



The bill of the Snowy Owl is formed on the same plan as 

 that of the Peregrine Falcon, although differing considerably 

 in its details, and in particular wanting the tooth-like process 

 of the upper mandible ; and the feet are similarly organized, 

 although covered with feathers. The tongue, Fig. 3, «, is 

 short, broad, and flattened above, the tip notched, the base, &, 

 deeply emarginate and papillate. The aperture of the glottis, 

 c, is destitute of papillce on the edges, but has two central coni- 

 cal papillae behind, together with two papillate flaps. 



Fig. 1. represents, besides the oesophagus, «, the tongue ; ^, 

 ^, the hyoid bones ; r, ^, the trachea, flattened, five and a half 

 inches long, composed of numerous narrow rings, with wide 

 intervals, and at the lower part of the neck dividing into two 

 bronchi, ^, e ; f\ the heart, with the pericardium removed ; <7, 

 /^, the right and left lobes of the liver. The stomach and intes- 

 tines are covered by the abdominal parietes, i ; but at j are 

 seen three of the large air-cells which are distributed through 

 the body. The oesophagus, 6, ^, /, is nine inches long. At the 

 commencement its diameter is an inch and a half, and it gra- 

 dually contracts to less than an inch, but enlarges to an inch 

 or a little more before entering the thorax, when it again con- 

 tracts. It differs therefore from that of the Peregrine Falcon 

 in having no crop ; but in other respects is similar, its coats 

 beinof of the same natm-e. 



