( S05 ) 
XVII. On the Organs of Voice in Birds. By William Yarrell, Esg. 
‘ F.L.S: 
Read June 2 and 16, 1829. 
Tux very liberal manner in which the Linnean Society did me 
the honour to illustrate a former paper on the Trachez of Birds, 
has been an additional inducement with me to render this sub- 
ject as complete as my means of observation would allow: I 
therefore now submit descriptions and figures of the numerous 
muscles attached to the different parts of the windpipes of birds, 
by the action of which their varied and extraordinary powers of 
voice are produced, with representations of the trachez of four 
birds, which, though not all entirely unknown, are each of them 
illustrative of a portion of this subject, and have not been 
hitherto so represented as to afford a correct idea of their local 
situation or peculiarities. 
The organ of voice in birds may be considered as consisting 
of four parts; the glottis or superior larynx, the tube of the 
trachea, the inferior larynx with its muscles, and the bronchise ; 
and the variety of modulation birds are known to possess has its 
corresponding variety of forms. The glottis or superior le M " n 1 
opens into the mouth at the root of the tongue, The 
long and narrow, encircled by two pair of muscles which govern 
the size of the aperture, and constitute one of the accessory 
means by which the sound of the voice is regulated. Birds 
have no epiglottis or covering over this aperture to prevenim y 
2R2 p? 
