THE RESPIRATORY SYSTEM, 211 
of the uppermost part of our own trachea, which is called the 
larynx. In us this is the organ of voice, but it is not so in 
Birds. 
The windpipe of Birds is kept in the form of an open tube 
by a numerous series of generally complete bony rings in its 
substance. It is very long and often convoluted, sometimes 
making a coil within the sternum, and sometimes possessing 
subcutaneous dilatations, as in the Emeu, where some of the 
Fig. 162. 

Syrinx oF Raven. 
Lowest part of trachea and roots of the two bronchi. 
a, Front half-ring of bronchus ; 4, second (more moveable than the first) ; 
¢, third half-ring—connected with the second by ligament and 
membrane. 
rings are incomplete in front. Inthe Penguin the trachea has 
a longitudinal septum. At its lower end the trachea bifurcates 
and its two branches, which lead into the lungs, are called 
bronche. 
The organ of voice in Birds is called the syrinw or lower larynx, 
because it is placed much lower down than our own organ of 
voice. Indeed, such a structure as the “ syrinx ” is absolutely 
peculiar to the Class of Birds. Its general condition is as 
follows. It is formed by the coalescence and modification in 
shape of the lower rings of the trachea and the upper rings of the 
bronchi, the latter being incomplete internally, so that the sides 
Be 
