TRACHEA OF PIGEONS AND PTARMIGANS. 31 



processes, one in front, the other behind, the intervening space 

 being filled by an elastic membrane, which when relaxed be- 

 comes concave externally, but which may be rendered tense 

 by the action of the muscles, h /«, inserted into it. 



Fig. 2 is a lateral view of the syrinx, shewing the lower part 

 of the sterno-trachealis muscle, a ; the tensor of the membrane 

 of the syrinx, h ; that membrane itself, c ; with its upper and 

 lower rings. This lower ring of the trachea, Fig. 1, g, has no 

 division, like the corresjDonding part in the Rook and Black- 

 bird, PI. X, Fig. 7, and PL XI, Fig. 14 ; but the membranes 

 of the bronchi merely meet there, and are united by a dense 

 layer, the ring. Fig. 3, remaining entire. On blowing into the 

 bronchi, we find that a tremulous murmuring sound is pro- 

 duced, which we may fancy to resemble that of the bird, al- 

 though we are unable to modulate it. 



In Fig. 4 are seen, the upper surface of the tongue, a ; the 

 hyoid bones, h h ; the aperture of the glottis, with its pad, c ; 

 the first rings of the trachea, d ; and part of the contractor 

 muscles, e e. 



Fig. 5 shows the bones of the larynx : namely, the thyroid, 

 a ; the appendages of the thyroidj h b ; the cricoid, c ; and the 

 arytenoid, d. It is here to be observed that the appendages of 

 the thyroid, which by many anatomists have been considered 

 as portions of the cricoid bone, are actually continuous with the 

 body of the tliyroid^ although reduced to a cartilaginous state. 



Figs. 6 and 7 shew the difference in the thickness of the 

 same rings, Fig. 6 being a posterior. Fig. 7 an anterior view. 



The muscles of the larynx are reduced to two, namely, the 

 thyro-arytenoideus, and the thyro-cricoideus, on each side. 



The differences here presented are important and very ob- 

 vious, and would induce us to suppose that the more simple the 

 voice, the less complex, as to its muscular apparatus at least, 

 the lower larynx. But, before we come to general laws, we 

 must extend our observation, and therefore, considering that 

 some ornithologists would force upon us the Pigeons as part of 

 the Rasores, let us examine the windpipe of a Gallinaceous bird, 

 and see whether or not it differs as much from that of a Cooer, 

 as many of the other organs of these two most distinct orders do. 



