]G(i 



AJklEltlCAJv' BrriERN. 



After examining tlio vocal organs ilescribeil, with the results in licateil. I was not surprised, upon lookinp^ 

 at the inferior larynx, to find that the usual sound-producing apparatus here was nearly functionless, and 

 evidently only used to give utterance to the harsh note that the Bittern emits at times upon rising when 

 disturbed. The sterno tracheal muscle, fig. 30, A, B, C, D, and fig. .'U, k, that acts as a retractor for the 

 vibrating, or tympaniform, membrane, is not particularly well developed. The tyrapanif jrm membrane. 

 fig. 30, A and B, o, although broail, is thick and incapable of munh vibration, and finally, the bones which 

 make up the body of the larynx, ib. A, ami B, ai'e short and. on the sides, are fused together, as seen in ib. 

 D. I have given figures of the lower laryn.x, to show a peculiar modification for jireventing too great 

 pressure against the inside of the bronchial tubes, by the distended lower portion of the gullet, w Inch passes 

 between them. Although the air is cut off, in a great measure, f.-om this portion, by tlie scapular attach- 

 ment of the large compressing muscle, fig. 34, t, yet there must be considerable inflation of this part. As 

 Been in fig. 3!», G, the bronchial tubes are considerably widened, even on the upper side, and below, their 



D 



Fi(i. 311. Inferior larynx of American Bittern, male, life size ; m. trachea ; t, tracheal muscle ; sterno 

 trachealis ; a, t, bony portion of larynx ; o, tymiianif )rm membrane ; n, lungs. 



width is no less. On the under side of each tube, there is a swollen portion, made up of a hard, rather 

 fibrous substance. This is the portion colored pink in fig. 30, A, B. This elevated portion comes in C(jntact 

 with the gullet and prevents it from pressing against the tympaniform membrane. Fig. 3i), A, shows the 

 lower side of the larynx, C. the uiiper side ; B, is the inside of the left bronchial tube, the right side being 

 removed at this junction with the trachea, e. Ib. D, shows the outside of the same tube. All the figures 

 are the size of life. Other references not given, are as follows : m, trachea ; t, beginning of slight bronchial 

 muscle, best seen in fig. D, between m and a : c. bronchial tubes ; and n, position of lungs. 



SUMMARY. 



I give below a summary of the variinis modifications that the organs of the American Bittern have 

 vmdergone in order to produce the pumping notes. I do not wish to be understood to say that the muscles 

 given are positively new to science, but that the functions to which they are here applied, have never been 

 noticed, and that they have become so modified in order to perform these functions, as to warrant the 

 applications which I have given them. I have never noticed anything of the kind among other Herons, and 

 a pair of Least Bitterns, Ardetta exilis. taken at Wayland. June 10th of this year, did not, u])on carcfu] 

 examination, show even a rudiment of the peculiar vocal muscles, and they were about to breed. 



