RAVEN. 75 



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 accommodate the tube to all the varied move- 

 ments of the neck : they influence the length of the trachea, 

 as well as that of the bronchige, and on account of their place 

 of insertion have been named stern o-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 the 

 merry-thought, or forked bone, and have been named in conse- 

 quence furculo-tracheal ; but this division does not appear to 

 afford any additional powers of voice. In figures 1 and 2, let- 

 ters a a refer to the tube \ bh to the point of division, or bone 

 of divarication ; c to the bronchia, and </ to the elongated 

 muscles going off to be attached to the sternum. Another 

 example of two pair of muscles at the inferior larynx is found 

 in the family of the Pigeons, as represented in the third 

 figure of this third group. The second pair in this instance, 

 marked -e, are formed of a portion of the sterno-tracheal mus- 

 cles, but taking a diflferent direction. They proceed by a 

 narrow slip, from that point upon the tube where the first 

 pair of muscles go off to be inserted upon the sternum down 

 the side of the trachea, to be attached externally to the mem- 

 brane between the lowest ring of the tube, and the first ring 

 of the bronchia, as shown in the side-view before referred to. 

 By their contraction they shorten the flexible portion of the 

 tube between their points of attachment, and produce ten- 

 sion upon the viembrana tympaniforviis. 



Among British Birds I have found no examples with three 

 pair, or four pair of muscles, at the inferior larynx ; I pro- 

 ceed, therefore, to the consideration of the most complex 

 organ, — that furnished with five pair. 



The birds included in this division are all those of the 

 family of the Crows, the Starling, the Thrush tribe, the 



