RAVEN. 



71 



tubes producing notes low in the scale of tones, and 

 vice versa. The substance of the tube itself has also to be 

 considered, though some anomalies present themselves. 

 Those birds possessing strong and broad cartilages, or bony 

 rings, have monotonous and loud voices ; while the more 

 slender rings, with enlarged spaces between them, allow a 

 freedom of motion, producing a corresponding variety 

 in the scale of tone. 



The inferior larynx, the true situation of the organ of 

 voice in birds, as the experiments of Baron Cuvier have 



