ORGANS OF VOICE AND RESPIRATION. Ill 



voice is produced, constitutes a special peculiarity of the class of 

 Birds. It is situated in the upper part of the thoracic cavity at 

 the extremity of the trachea, where that divides into the two bron- 

 chi. The length of the inferior larynx is mostly greatest from be- 

 fore backward, and its interior forms a quadrangular cavity, which 

 is generally divided inferiorly (at its outlet) by a cross-bone pas- 

 sing from, before backward, into two lateral halves, that receive the 

 two openings of the bronchi, which are to be viewed as forming a 

 double rima glottidis. The cross bone consists of the last tracheal 

 ring increased in size, or else of several rings which have be- 

 come firm and rigid, approximated and even blended together, so 

 as to form a firm bony drum of variable size. The commencement 

 of the bronchial tubes is also to be regarded as forming part of the 

 inferior laryngeal apparatus, since their first rings and the mem- 

 branes which unite them must exert the greatest influence upon the 

 production of the voice. 



As might be expected from the great variety of character which 

 the voice of Birds presents, the structure of the inferior larynx in the 

 several genera and species offers for our study a very extensive series 

 of modifications. In some cases this larynx appears to be entirely 

 absent, there being neither expansions of the trachea nor vibratory 

 membranes to produce, by combining in action with the lingual ap- 

 paratus, any kind of sound, so that voice may be said to be totally 

 deficient. These conditions are exemplified in both the Black and 

 White Stork. The rings are very soft and cartilaginous through- 

 out the whole extent of the trachea, arid there are no indications 

 whatever of a larynx at its bifurcation ; and as little of an internal 

 and external tympanic membrane, or even of a single pair of mus- 

 cles. The bronchi are long, and formed, like the trachea, of nume- 

 rous (about 50) entire rings, the intervals between which are car- 

 tilaginous, so that the bronchi form soft but elastic cylindrical tubes, 

 which become membranous so soon as they enter the substance of 

 the lungs. The storks, as is known, with the exception of a clat- 

 tering noise produced by the bill, give utterance to no distinct tone, 

 but only a feeble hiss. The muscles of the inferior larnyx are want- 

 ing in the Struthious birds, several Grallae and Natatores, and in 

 the Gallinse and Owls; the bronchi are partially surrounded by 

 segments of rings, and completed by membrane on their internal 

 side. 



From the preceding examples we pass to those Birds, as the true 

 Vultures, which have been also stated, though incorrectly, to possess 



