GENESIS OF BIBD-SOMG. 95 



the other cord being a membrane developed 

 on the inside of the bronchial rings, or rather 

 half-rings, opposite the septum or partition 

 above mentioned. Thus a column of air 

 I)assing from the lungs to escape through the 

 trachea sets these membranes to vibrating, 

 whilst by means of five or six pairs of deli- 

 cately adjusted muscles the air space is 

 changed with wonderful facility, the column 

 shortened or lengthened, as is done by the 

 flute-player, and indeed the whole lower 

 throat becomes a generator of sweet sounds, 

 which, passing up to the bird's mouth, are 

 broken into melodious bits, so to speak, and 

 scattered to the winds; for the highest vo- 

 calization, although generated in the syrinx, 

 is made into song, in a large degree, by the 

 bird's tongue, its posterior mouth walls, and 

 the upper extremity of the trachea, all of 

 which taken together constitute a compli- 

 cated and perfectly adjusted governor of the 

 quantity, the accent, and, in a measure, the 

 quality of the notes. 



Every observer has remarked that nearly 

 all the superior songsters among birds have 

 rather long and slender bills, whilst the talk- 

 ers have short, stout ones. I have tried to 

 discover, and think I have discovered, the 

 relation that width, length, and curvatvire of 

 bill have to the quality or style of voice. It 

 is sufficient to remark here that birds having 

 extremely short, thick beaks, like that of the 

 cardinal grossbeak or that of the blue-jay, 

 have not the power, apparently, of trilling, 

 shaking, or quavering the voice (which is the 

 distinguishing gift of the thrush and many 

 other slender-billed birds), though the gross- 

 beak and the jay have excellent vocal pow 

 era. Eeduced to a rule, the comparison wiU 



