74 



CORVTD.E. 



and tlie voice of the bird monotonous. Tlie want of muscles 

 of voice will be more immediately apparent by comparing the 

 representation of No. 1 of the second group of these vocal 

 illustrations, with those of the Raven, with its five muscles 

 on each side, forming the fourth group. 



The next division, or those birds possessing but one pair 

 of muscles of voice at the inferior larynx, is by far the most 

 numerous, including as it does most of the Raptores, some of 

 the Insessores. all the Rasores, Grallatores, and Natatores, 

 with a few exceptions, which will be pointed out. The 

 British species of these orders are the examples more particu- 

 larly referred to. 



The single pair of muscles, when one pair only exist, arise 

 from the whole outer surface of the cricoid cartilage : descend- 

 ing, they form a sheath round the upper part of the tube, 

 afterwards dividing and passing downwards in two equal por- 

 tions, one on each side, uniformly attached to the tube, and 

 not quitting it till arrived at or near the bone of divarication ; 

 when separating from the tube of the windpipe, they pass 

 outwards and downwards in distinct slips on each side, to be 



