TRACHEA OF BIRDS. 



186 



voices ? For the longer a tube is, you know, in which 

 a sound is uiade, the lower will be its pitch. 



Dr. B. The fact is confirmed satisfactorily by ob- 

 se.'v tion, thnt in different birds, those have the highest 

 voices which h v the shortest wind-pipes, and vice versa. 

 In the vocal organs of birds, we find some curious 

 forms of structure, which so far as we are acquainted 

 with the subject, do not seem to have any particular 

 purpose. Some of the Gallinacea3 order, among which 

 we may mention the domestic cock, the pheasant, some 

 liver birds, some of the anseres, 

 as the swan, and some wild ducks, 

 have large inflated pouches con- 

 nected with the inferior larynx,and 

 communicating freely with it. 

 Here is the larynx of a wild duck, 

 differing very little, however from 

 that of our domestic duck. In 

 some river birds, the wind-pipe 

 is convoluted or coiled round upon 

 itself* Here is a specimen of this 

 structure in the wind-pipe of a 

 crane, where its convolutions are 

 contained with- 

 in the sternum 

 or breast-bone. 

 In some other 

 species howev- 

 er, it is not en- 

 closed in the 

 sternum. What 

 is a little re- 

 markable, this 

 structure is fre- 

 quently posses- 

 sed by one sex. 

 and not the other, of the same species. The voice in 

 nearly all those birds whose wind-pipe is convoluted in 

 16* 



