THE ANATOMY OF BIRD-SONG. Ill 



above the point of bifurcation. In other 

 words, imagine the hollow of the syrinx (lower 

 end of the straw) divided into two equal 

 apartments by a thin vertical wall, whilst 

 from each apartment passes a smaller tube 

 just like the trachea (the straw). Such is a 

 general description of what has heretofore 

 been considered the song-organ of the highest 

 kind of bird. I cannot do better, however, 

 than to add here a condensation of the de- 

 tailed description prepared by Prof. Huxley : 

 1st, The trachea is a hollow cylinder formed 

 by bony rings. 2nd, "The hindermost (lowest) 

 rings of the trachea coalesce and form a pe- 

 culiarly arranged chamber immediately be- 

 yond (below) which the bronchi diverge, and 

 from their posterior wall, where one bronchus 

 passes into the other, a vertical fold of the 

 lining membrane rises in the middle towards 

 the tympanum (syrinx chamber) and forms a 

 vertical septum between the anterior aper- 

 tures of the two bronchi. The anterior edg^ 

 of this septum is a free and thin membrana 

 semilunaris, but in its interior a cartilagin- 

 ous or osseus frame is developed and becomes 

 united with the tympanum. The base of this 

 frame sends out two cornua, one along the 

 dorsal, the other along the ventral edge of the 

 inner wall of the bronchus of its side, which 

 in this part of its extent is membranous and 

 elastic, and named the membrana tympani- 

 formis interna. Opposite this the bronchial 

 rings are incomplete, and have the form of 

 arches embracing the outer moiety of the 

 bronchus. The second and third of these 

 bronchial arcs are freely movable, and elastic 

 tissue accumulated upon their inner surfaces 

 gives rise to a fold of the mucous membrane 

 which forms the outer boundary of a cleft, 

 bounded on the inner side by the membrana 

 semilunaris. The air forced through these 



