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NEW YORK STATE MUSEUM 



marked on page 225, volume 2 of his Comparative Anatomy and 

 Physiology of Vertebrates, " In the males of the mergansers and of 

 niost ducks a certain number of the terminal rings of the trachea 

 are welded together and expanded into an irregular bony case, di- 

 vided into two unequal cavities. In the Mergus serrator, 

 the broad ' p&ssulus ' leaves a passage at its upper part by which 

 the air from the right bronchus can pass to and from the trachea : 

 part of the outer wall of the right laryngeal chamber is formed by 

 membrane, this chamber is extended by the osseous cavity. A 

 similar but somewhat more complex lower larynx exists in the male 

 Anas clang u la. These modifications relate to the power 

 rather than to the variety of the voice." 



Coues in the fifth edition of his 

 " Key " [p. 207, 208] speaks of 

 the trachea as '' the tube whicli 

 conveys air to and from the lungs. 

 It commences at the root of the 

 tongue by a chink in the floor of 

 the mouth, runs down the neck in 

 front between the gullet and the 

 skin, and ends below by forking 

 into right and left bronchus. It 

 is composed of a series of very 

 numerous gristly or bony rings 

 connected by elastic membrane. 

 When contracted (by certain mus- 

 cles, the rings look like an alternat- 

 ing series of lateral half loops, as 

 in figure 29, a; when stretched to 

 the utmost, as in figure 29, b, they are clearly seen to be annular, 

 or completely circular. The curious beveling of the right and left 

 sides of each ring alternately is shown in figure 30, 1,2; and figure 

 30, 2, I represents the same two rings put together. The principle 

 by which any two rings slip partly over each other on alternate 

 sides is something like that upon which a cooper fastens the ends of 

 any one barrel hoop without any nailing or tying. The rings are 

 in some birds perfectly cartilaginous ; in most they become osseous." 

 (It is the case in all the Anseres I have examined.) 



" The most remarkable expansions of the lower part of the tube 

 occur in many sea ducks and mergansers (Fuligulinae and Mer- 

 ginae), and some other birds; several lower rings of the trachea 



Fig. 28 Bony labyrinth at the pul- 

 monic extremity of the trachea of male 

 CI angula islandica, seen upon 

 posterior aspect. Natural size 



