CLASS AVES. 7 



The ear of birds has but one little bone between 

 the tympanum and the oval aperture. Their cochlea 

 is a cone scarcely bent ; but their semicircular canals 

 are large^ and lodged in a part of the skull^ where 

 they are surrounded on all sides with air cavities 

 which communicate with the area. Night-birds alone 

 have a large external ear^ which, nevertheless, is not 

 so prominent as that of quadrupeds ; this opening is 

 generally covered with barbed feathers^ more fringed 

 than the others. 



The organ of smell, hidden in the base of the beak, 

 has commonly only three cartilaginous cornets, which 

 vary as to their complication ; it is very sensible, 

 although it has no sinus dug into the skull. The size 

 of the osseous openings of the nostrils governs the 

 form of the beak ; and the cartilages^ membranes, 

 feathers, and other teguments, which straiten these 

 openings, have an influence on the strength of the 

 smell, and on the sort of nourishment. 



The tongue has little muscular substance, and is 

 sustained by a production of the hyoid bone : it has 

 but little delicacy in the majority of birds. 



The feathers, as well as quills, which differ from 

 them only in size, are composed of a stem, hollow 

 at the base, and of barbs, each having others much 

 smaller ; their tissue, their brightness, their strength, 

 and general form, vary infinitely. Touch must be 

 weak in all the parts capable of it ; and as the beak 

 is almost always corneous, and possessed of little 

 sensibility ; and the toes are covered with scales on 



