110 THE ANATOMY OF BIRD-SONG. 



has given the subject thorough analysis at 

 first hand. 



Let us now examine the avian syrinx with 

 a view to settling the question whether or not 

 it is a song-making organ. In doing this we 

 will choose the syrinx of an accomplished 

 singer, so that there may be no doubt in the 

 matter. 



In making my dissections and other studies 

 I began with the mocking-bird and ended 

 with the wood-thrush, branching out between 

 these to take in many birds not singers at all. 



The syrinx of the mocking-bird will serve 

 our purpose just now. 



III. 



The syrinx of the mocking-bird is situated 

 in the cavity of the bird's breast near the 

 upper part of the lungs and it is made up of 

 the following parts : A slight enlargement of 

 the lower rings of the trachea, forming a 

 drum divided internally at its posterior ex- 

 tremity by a bony cross-piece called the pes- 

 sulus, a membranous cartilage rising above 

 the pessulus a little way into the trachea 

 proper, dividing the hollow thereof into 

 halves, and a wisp of delicate muscles. The 

 trachea forks at the lower part of the syrinx 

 into, two bronchial tubes that pass directly to 

 the lungs right and left. 



The reader may get an excellent idea of a 

 mocking-bird's trachea and syrinx by imag- 

 ining for the trachea a hollow large-sized 

 broom-straw an inch and a half in length, one 

 end of which is the glottis, and the other end, 

 slightly enlarged, the syrinx, out of which 

 the bronchial tubes pass at an angle with each 

 other of some fifty degrees. Further, imagine 

 this bifurcated lower end of the broom-straw 

 to be furnished with a valve-like division- 

 wall rising a little way up its hollow, just 



