. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 1500 VOICE. larynx differs in structure from that ofany other order of birds. They have no os transversale dividing the vocal organs, which is conse- quently a single larynx. The segments of the rings in which the lower end of the trachea terminates are consolidated together on each side. The last two of these segments are of a crescent-like or semilunar form, with its axis nearly perpendicular to the axes of the ring of the trachea; they are concave to each other, and their extremities articulated together, forming an e
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. 1500 VOICE. larynx differs in structure from that ofany other order of birds. They have no os transversale dividing the vocal organs, which is conse- quently a single larynx. The segments of the rings in which the lower end of the trachea terminates are consolidated together on each side. The last two of these segments are of a crescent-like or semilunar form, with its axis nearly perpendicular to the axes of the ring of the trachea; they are concave to each other, and their extremities articulated together, forming an elliptical space which is furnished with a thin vibratile membrane, as seen in fg. 917. At their junction is the joint or axis on which they revolve upon each other, and by which the tension of the mem- brane of the glottis is capable of being varied. Fiz. 917. voluted trachea are found in the Gal- linaceae ; as in the RhyncluEa Australia, and Phasianus Purraqua. In the singing birds the trachea is a cylindrical tube; the rings which are at first cartilaginous become ossi- fied with age. The tracheal rings, which are entire in the adult state, being connected by elastic membranes, are at a sufficient distance from each other to allow of all the movements of the neck. Fig. 918. Inferior L'jtrynic uf the Parrot. a, b, tensors of the glottis; r, laxator of glottis. The glottis is formed on each side by the elastic membranes that fill the space between the semilunar bones); these membranes leave a narrow chink between them through which the air from the lungs passes, and puts them in a state of vibration whenever the bird draws them sufficiently tense ; for this pur- pose they are provided with three pairs of muscles, of which two a, b, are tensors, and one c laxator of the glottis. The trachea of birds comprehends that portion of the vocal tube which lies between the superior and inferior larynx ; its diameter and length generally depend on the length of the neck of the bird. In t
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