RAVEN. 75 



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 tension upon the mem- 

 brana tympaniformis. 



Among British Birds I have found no examples with 

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

 proceed, 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 

 Warblers, Larks, Buntings, Finches,* Swallows, &e., the 

 organs of voice in which vary only in size. In birds pos- 

 sessing powers of song, or imitation, the tube of the trachea 

 is nearly uniform in shape throughout, the bronchise long in 

 proportion, and both parts perfectly flexible. The fourth 

 group here introduced exhibits, fig. 1, a front view fig. 2, 

 a back view and fig. 3, a side view of the lower portion 

 of the trachea and its muscles in the Eaven, which may be 

 considered the type of this form, and from its size admits of 

 clear explanation. Figures 2 and 3 of the second group, 

 page 69, exhibit an outside and an inside view of the same 

 part, but divested of its muscles, to show by the prevalence 

 and interposition of membrane, the degree of alteration the 

 various muscles are able to effect. 



Referring again to the fourth group, on the opposite 

 page, the pair of muscles which descend on the outside of 

 the trachea, divide at a short distance above the end of the 

 tube, and one portion is directed in continuation downwards 

 and backwards, to be inserted upon the extreme posterior 



* The Canary is a true Finch, possessing, like the best Song Birds, five pair 

 of true muscles of voice, and hence arises its power of imitating other sounds, as 

 evinced in the Canary, which has for some time past formed an interesting sub- 

 ject of exhibition in London. 



