RAVEN. 77 



No. 1 is a representation of the lower portion of the trachea 

 of a Vulture, without muscles, or any true bone of divari- 

 cation, 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 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 particularly referred to. 



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

 arise from the whole outer surface of the cricoid cartilage : 

 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 divarication; when separating from the tube of 

 the windpipe, they pass outwards and downwards in dis- 

 tinct slips on each side, to be inserted upon each inner 

 lateral edge of the breast-bone or sternum ; third group, 

 figs. 1 and 2, front and side view. This pair of muscles 

 support and strengthen the windpipe, and serve to ac- 

 commodate the tube to all the varied movements of the 

 neck : they influence the length of the tracheae, as well as 

 that of the bronchiae, and on account of their place of 

 insertion have been named sterno-tracheal. This pair of 

 muscles sometimes send off a small slip towards the bottom, 

 which is inserted upon the inner surface of the bone called 



