The Breath of a Bird 167 
The swollen rim of this opening suffices to close it, and 
there is no elaborate trap-door arrangement as in mam- 
mals, only a few backwardly directed fleshy points. 
Birds have no trace of an ‘‘Adam’s apple.” The vocal 
chords and other adjuncts to the voice of mammals 
are entirely absent in birds, not a single note or song 
being produced in the upper 
throat. 
Passing down the neck 
from this orifice is the wind- 
pipe, follows the 
course of the cesophagus, or 
which 
food canal, passes to one 
side of the crop and _ be- 
tween the two branches of 
the wish-bone, and _ finally 
divides into two equal parts 
called bronchi, which carry 
the air directly to the lungs. 
Comparison of the two 
Fie. 127.—Windpipe and cesophagus of 
bird compared; the former always dis- 
tended; the latter soft and collapsed. 
tubes which traverse the 
throat and neck of birds shows them to he very different 
in appearance and structure, and consideration of their 
respective functions gives us the key to this dissimilarity. 
The only occasion for the cesophagus to open is to nerinité 
the passage of food, and thus a limp, fleshy canal answers 
all requirements. The windpipe, on the contrary, must 
always be wide open, and not only this, but it must he kept 
open no matter what the pressure upon it. In addition, 
it must be flexible, yielding to every motion of the neck, 
