VELVET SCOTER. 



219 



hollow bony enlargement situated about two-thirds down the 

 tube, made up of expanded tracheal rings, which in the 

 adult bird are firmly ossified together. Upon each side of 

 this enlargement a small muscle passing downwards is inserted 

 upon the inner side of the shaft of the bone, called the 

 merrythought ; and the voice is probably influenced by the 

 action of these muscles altering the relative position of this 

 hollow bulb upon the tube. There is also another pecu- 

 liarity. On making a longitudinal lateral section, as shown 

 in the outside figures below, it will be seen that the inner 

 tube of the trachea, at its upper part, has an aperture on each 

 side by which it communicates freely with the cavity within 

 another bony enlargement, situated immediately below the 

 superior larynx, and brings to mind the laryngeal cavities 

 found in some of the higher animals. A slip of paper is 

 represented as passing through both apertures. 



WiiA 



