12 



PASSERES. 



Ihe classification of the Passeres — as witness tlie Tracheophonw. 

 Briefly three types of syrinx are recognized — tlie 'J'racheo- 

 bronchial, the Tracheal and the Eronchial, the last two being 

 derivatives of the first. The tracheo-broiichial is the type found 

 in the Oscines and Sub-Osciiies. Herein the lower end of the 

 trachea has the last fonr or five rings welded to form a little dice- 

 shaped box communicating below with tlie bronchi. The 

 bronchial rings I and II are closely attaclied to this box, 

 while III forms a strong arcuate bar supporting a delicate 

 sheet of membrane stretched between rings I and II on the 

 one hand and YV on the other. The bronchial rings ai-e in- 

 complete on their inner aspects, their free ends supporting a 

 " tympanic memlirane," wliich plays an important part in voice 



6 ■•.,1 ~™ 



Syrinx of a ilagpie, showing the Diacroinyodian attaclinieut of ilie intrinsic 

 muscles at the ends of the bronchial semi-rings. Tlie lel't-hanil figure is a side 

 view and the right-liand figure a dorsal vieve of (be syrinx. The memltranous 

 parts between thebroncliial semi-rings and the internal tyuqianiform membrane 

 are dotted ; II, III are the second and third bronchial semi-rings; T.i, tlie 

 internal tynipaniform membrane ; i^t, tiie muscle from the side of the trachea 

 to the upper end of the clavicle; 1, 2. 3, 4, 5, 0, the syringeal muscles ; there 

 is a 7tli, which is hidden by the Gth ; tlie 4tli is hidden below and between the 

 1st, 2nd, and 3rd. 



production. At the junction of the bronchi with the trachea is a 

 bony bar — the " pessulus." This supports a thin fold of mem- 

 brane whose free edge cuts across the bottom of the dice-sbaped 

 box of the tracheal tube. By its vibrations it acts like the "free 

 reed " oT an organ-pipe. Muscular lips extending from the 

 inner surfaces of bronchial semi-ring III narrow the aperture on 

 either side of the "reed" during the production of the " A'oice " 

 or song, and thus complete the mechanism of voice production. 

 In tlie Tracheal syrinx a variable number of the lower tracheal 



