156 PRACTICAL ORNITHOLOGY. 



The Ear. — In the Buzzard, as in all the birds of the Fal- 

 conine family, the external aperture of the ear is of an elliptical 

 form. Its margin is fringed with slender feathers, of which 

 the anterior lie over and protect it from injury, or prevent 

 the entrance of dust or other objects. From this external 

 fringed aperture. Fig. 2, a b, which we slit open behind, there 

 proceeds obliquely backwards a short passage, the Meatus 

 auditorius externus^ having at its base anteriorly an elliptical 

 space, c, covered with skin. Immediately behind this, and 

 placed obliquely so as to incline backwards and outwards, is a 

 delicate, semitransparent membrane, d, of an elliptical form, 

 about four and a half twelfths of an inch in its greatest dia- 

 meter, convex externally, or rather presenting the appearance 

 of a short cone, its apex being supported by a small bone placed 

 internally. In the natural state of the parts, this membrane is 

 concealed by a muscle, e, inserted into the lower jaw, and here 

 cut across and put aside. From its resemblance to the parch- 

 ment of a drum or tambour, stretched in a circular frame, it is 

 named the Memhrana tympani. Behind it is a cavity, of the 

 same width at first, but gradually, though irregularly narrow- 

 ing. This cavity, named the Tympanum, or drum of the ear, 

 is lined with a delicate membrane, and, although closed by the 

 membrana tympani externally, communicates with the external 

 air by means of a bony canal, the Eustachian tuhe^ which opens 

 into the hind part of the posterior aperture of the nares. It 

 also communicates by three apertures with the cells in the sub- 

 stance of the cranium, and by two is connected with the more 

 internal parts of the organ. The cavity of the tympanum con- 

 tains air. There is situated in it a slender bone, of which the 

 base, a roundish flattened disk, fills one of the two apertures 

 above mentioned, while the tip, having three cartilaginous pro- 

 cesses attached to it, rests against the membrana tympani, and 

 causes it to protrude. It is moved by a slender muscle attached 

 to its outer extremity, and counteracted by two tendinous cords. 

 The internal cavity of the ear, which is filled or bedewed with 

 an aqueous fluid, is of an irregular form, and communicates 

 with three curved bony tubes, lined with a membrane, and 



