Appendix 287 



lungs. Thus the whole cavity acts as a sound-chamber, 

 and is subject to tension and vibration together with 

 the "reed." 



2. Exactly opposite to the bony bar on each outer 

 side of this sound-chamber, and supported by one of 

 the half-rings just mentioned, there seems to be what 

 Mr. Pycraft describes as a fleshy fold. I use the 

 singular number, because in freshly-killed specimens Mr. 

 Pycraft has only been able hitherto to find one, though 

 in some books it is represented as double. These folds 

 can hardly be, as some seem to have thought, the 

 equivalent of the vocal cords in the human being ; they 

 do not seem to be sufficiently membraneous or import- 

 ant to generate musical sound independently. What 

 then is the function they perform ? In order to try 

 and answer this question I called Mr. Woods into con- 

 sultation. He suggested that their use might be either 

 to vibrate in sympathy with the " reed," like the sym- 

 pathetic strings of the old viola d'amore, or to help in 

 increasing the tension of the sound-chamber, or to 

 direct the wind upon the reed by narrowing the two 

 passages of the bronchi immediately below it. In order 

 to determine if possible which of the three guesses was 

 the most probable explanation, Mr. Woods and I paid a 

 visit to the Museum and examined a trachea and 

 syrinx which Mr. Pycraft had ready for us. They 

 happened to be those of a jay, — of all birds the most 

 unmusical ; but if the apparatus of this bird is in the 

 main like that of most others, the fleshy folds are 

 placed just below the "reed " (opposite to the bony bar 

 on which the reed rests), a position which would cer- 

 tainly suggest our third explanation. On that hypo- 

 thesis the folds would act as a kind of lips, compressing 

 the currents of wind in the two bronchi, and directing 

 them with greater force and efi'ect upon the vibrating 

 membrane which I have called a reed. 



