vi FORM AND FUNCTION 139 



and that of an unmusical bird is that the muscles 

 of the former are, in most cases, more numerous and 

 stronger. The syrinx of the Skylark is almost a ball 

 of muscle, whereas the Pigeon's has but very little 

 to show. But it is very remarkable how muscular a 

 syrinx some few non-singers have. Among these arc 

 the Crow and the Raven. Perhaps a more striking 

 instance is that of the Bullfinch who sings very feebly 

 in the wild state. The hen-bird also, who, I believe, 

 is almost voiceless, has highly developed voice muscles. 

 In the cock-bird they have clearly not lost their power, 

 for in captivity he becomes a splendid vocalist. 

 However first-rate the syrinx and its muscles may be, 

 it is wonderful that so small a creature as, for instance, 

 a Nightingale, can produce such an amount of voice. 

 Even the Wren sends out a flood of powerful notes. 

 The Thrush's song is wonderful as a tour de force. 

 If the bird were nothing but a musical instrument, the 

 volume of sound sent forth would be astonishing ; and 

 when we consider the variety of functions which its 

 small body has to perform its musical powers supply 

 far greater reason for wonder. The air-sacks, no doubt, 

 are a great assistance. Those great reservoirs of air 

 must make it easier for the bird to avoid the awkward 

 crises that come to the untrained human vocalist 

 when he finds, at the moment his grandest notes are 

 expected of him, that his voice is becoming thin and 

 feeble for want of breath. The trachea sometimes 

 takes strange forms which might be thought to influ- 

 ence the voice. In the Drake, just in front of the syrinx, 

 it has a big box-like appendage, which looks as if it 

 might be intended to give the voice greater resonance. 



