VOCAL ORGANS OF LINNET AND WOOD PIGEON. 29 



same ring ; and lastly, the sterno-trachealis, ^, here extremely 

 delicate, which passes from the lower part of the trachea to 

 the edge of the sternum. Viewed from behind, the muscles 

 appear as in Fig. 10. The bronchial rings are eighteen. 



Such, then, is the apparatus by which the voice of the 

 Cantatores is attuned. The air contained in the lungs and 

 air-cells, passing through the bronchi, causes the vocal mem- 

 branes at their anterior extremity to vibrate, and thus produces 

 sound, which is rendered grave or acute by the relaxation or 

 tension of the parts ; and the stream of air thus thrown into 

 vibrations is divided, narrowed, or allowed to pass free, by the 

 muscles of the larynx. The modifications of these organs pre- 

 sented by the different species of this order, are slight, and in all 

 those which I have examined, I have found the same parts, and 

 the same number of muscles. The peculiar songs of different 

 species must depend upon circumstances beyond our cognition, 

 for surely no one could imagine that the Raven, the Hooded 

 Crow, and the Rook, require as complex an apparatus to pro- 

 duce their unmusical cries, as that which the Blackbird, the 

 Song Thrush, the Nightingale, and the Linnet employ in mo- 

 dulating their voice, so as to give rise to those melodies which 

 are so delightful to us ; and yet the knife, the needle, and the 

 lens do not enable us to detect any superiority in the Warbler 

 over the Crow. 



Having examined the vocal organs of a species of the Canta- 

 tores, and those of a species of the Vagatores, we may now 

 advert to the respiratory and vocal apparatus of the Deglubitores. 

 Taking a Common Linnet as a representative of the latter, we 

 observe that the parts in question present no very remarkable 

 differences. As is seen in Plate XI, Fig. 17, the trachea is 

 similar to that of the Blackbird, being a little flattened, and 

 tapering, with the muscles of the larynx and syrinx essentially 

 the same. Instead of being merely lateral, however, the con- 

 tractor trachese is spread over its whole surface. The rings of 

 the trachea are about sixty, and the half rings of the bronchi 

 about twelve. 



The vocal organs of the Deglubitores, Vagatores, and Canta- 

 tores, are thus essentially similar, and occupy the highest place 



