318 Mr. YARRELL on the Organs of Voice in Birds. 
or compass of voice, than those provided with five pair ; but it 
will be seen by a reference that the insertion of the principal 
muscle shortening the bronchial tube, in the Parrots is much 
lower down than in any other birds; nor do any of the song- 
birds possess the power of altering the size of the aperture at 
the bottom of the tube of the trachea. Considerable advantage 
is supposed to be afforded the Parrots by their soft, fleshy, 
human-like tongue; yet it cannot be denied that the Raven, 
Magpie, Jay and Starling produce a close imitation of the 
human voice with tongues ER slender and horny. The cele- 
brated Mocking-bird of America, which I have once had an 
opportunity of examining, has an organ of voice and tongue 
precisely similar to our own Song-thrush. 
The organs of voice in the Mammalia, possessing chorde vo- 
cales, have been considered to bear some relation to musical 
instruments with strings; and those of birds, to wind instru- 
ments. Among the latter, (with most of which there are some 
- points of similarity,) they appear to me to have a closer resem- 
blance to the French horn than any other; the bronchiz per- 
forming the same office as the lips of the musician, and the 
muscles of the glottis, like the hand, governing the extent of 
the other aperture. The voices of the Stanley Crane and De- 
moiselle, with their single convolution in the trachea, are lower 
in the scale of tone than those of the other species of the same 
family having no such convolution; and the Common Crane 
with his elongated double convolution possesses a voice still 
deeper than the Stanley Crane or Demoiselle. In this circum- 
stance they also particularly resemble the French horn, the 
pe formers upon which fix additional circles of tube upon their 
istrument when required to take a part in any concerted pce 
üsic that is set i ina i low key. 
It will perhaps bi be objected, that the utmost priait of motion 
which 
