Mr. YannELL on the Organs of Voice in Birds. — 307 
uses to which the two processes already described are sub- 
servient, and the action and effect of the muscles attached to 
them, render it difficult for me to speak of them under any 
better designation. 
The tube of the windpipe is composed of two membranes, 
inclosing between them numerous cartilaginous or bony rings, 
forming a cylinder more or less perfect from end to end. Ossi- 
fication appears to commence in these rings at the front of the 
trachea, from which point the bone gradually extends equally 
on both sides towards the cesophagus as the bird increases in — 
age: in particular parts, however, of the trachez of some birds 
the rings are not entirely complete at any age. Various in- 
equalities of size occur in different parts of the same tube in 
some species, producing, as might be expected, a particular 
effect on the voice, to be hereafter explained ; and the length 
of the tube deserves consideration. "Thus, shrill notes are pro- 
duced by short tubes, and vice vers; the first are possessed by 
the Singing Birds, and the reverse by the Waders and Swimmers; 
but the diameter of the tube has also its influence, large tubes 
. producing notes low in the scale, and vice versá. The substance 
of the tube itself has also to be considered, though some ano- 
malies present themselves. Those birds possessing strong and 
broad cartilages or bony rings have monotonous and loud voices, 
while the more slender rings with enlarged spaces between them 
allow a freedom of motion producing a corresponding €: in 
the scale of tone. up 
"The inferior larynx, athe: Tm situation " the organ of voice in 
birds,—as the experiments of Baron Cuvier have sufliciently 
proved,—is situated at the bottom of the tube, and is formed 
sometimes by the approximation of several of the lower rings of 
the trachea more or less firmly ossified together, and occasion- 
ally of solid bones; varying in form, being com presai reoni- - 
