Mr. Yarkell on the Organs of Voice in Birds. 309 



of the lower portion of the trachea of a Condor Vulture without 

 muscles or any true bone of divarication, the bronchial rings 

 almost completing the circle, with little flexibility, and the voice 

 of the bird monotonous. The want of muscles of voice will be 

 more immediately apparent by comparing this representation 

 with those of Tab. XVIII, all of which exhibit various mus- 

 cles attached. The Spoonbill is another instance of a bird 

 without any true muscles of voice. Tab. XIX. is a representa- 

 tion of part of the inside of this bird with the convolutions of its 

 singular trachea m situ : the insertion of the bronchiae into the 

 lobes of the lungs is shown, but no ossification at their junction 

 with the tube of the trachea will be observed, nor any muscles 

 by which variations in the length of the trachea or bronchiae can 

 be effected. The convolutions of the trachea of the Spoonbill 

 have been described, but I am not aware that they have been 

 figured. 



The next division, or those birds possessing one pair of mus- 

 cles of voice, is by far the most numerous, including as it does 

 the genera Falco and Strix, some of the Insessores, all the 

 Rasores, Grallalores, and Natatores, with a few exceptions 

 only, which will be pointed out. I refer particularly to the 

 British species of these different orders, as it is with them I am 

 best acquainted. 



, The single pair of muscles with which these birds are pro- 

 vided, arise from the whole outer surface of the cricoid carti- 

 lage ; descending, they form a sheath round the upper part of 

 the tube, afterwards dividing and passing downwards in two 

 equal portions, one on each side, uniformly attached to the tube, 

 and not quitting it till arrived at or near the bone of divarica- 

 tion ; when, separating from the tube, they pass outwards and 

 downwards in distinct slips on each side to be inserted upon 

 each inner lateral edge of the sternum. This pair of muscles 



support 



