APPENDIX. 



ON THE CONVOLUTIONS OF THE TRACHEA IN BIRDS. 



In preparing this work for the press I have been struck with the singular 

 convolutions of the windpipe that are to be found to a greater or less extent 

 (with a few remarkable exceptions) throughout the species which constitute 

 the well-marked natural family Gruidse. 



In working out the natural history of the different cranes, I endeavoured 

 by actual dissection, when I could obtain recent specimens, or by the study 

 of preparations in museums, to discover the amount of convolution in the 

 trachete of the different species. I then essayed to trace the connection 

 between the voice of the bird and the character of the windpipe, and I 

 finally came to the conclusion that the elongation of the windpipe (and the 

 resulting twisting and convolution if it is much elongated) was connected 

 with the deepness of the note and resonance of the sound of the voice. 

 Everyone is acquainted with an ordinary post horn, a keyless conical tube 

 open at both ends. To the smaller end of the tube the lips — which are in 

 this case the vocal organs — are applied, and a note is produced, the pitch 

 and loudness of which depend on the length of the tube. In a short tube 

 the note is high, the resonance small. If the tube is lengthened, as is done 

 in the horn of a mail coach, the note becomes lower, louder, and of greater 

 power of diffusion; and these alterations occur in proportion as the 

 elongation is carried out. But there is a practical limit to the length of a 

 straight horn, inasmuch as it becomes inconvenient to use, and difHcult to 

 carry without injury. In the French hunting horn this evil is got rid of by 

 twisting and convoluting the tube, which is curved around the body of the 

 huntsman who blows it. 



This is precisely analogous to what occurs in nature in the Cranes. In 

 birds the syrinx, or lower larynx, which is the chief organ of voice, is 

 situated in the interior of the thorax, where the two bronchi, one from each 

 lung, join the lower end of the windpipe ; it is here that the vocal cords are 

 situated and the sound is produced, its depth and resonance depending on 

 the length of windpipe along which the vibrations have to pass. 



In the Crowned Crane, Balearica clirysopelargus, these convolutions are 

 absent, and the sternum is of the usual character, the furcula or merry- 

 thought not being attached to the keel, although there is a very slight 

 depression in the base of the keel in front, where it joins the body of the 



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