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Mr. Y aRRELL on the Organs of Voice in Birds. 319 
which birds appear to possess the power of exercising over the 
various parts of their organ of voice, seems insufficient to ac- 
count for the effects produced ; but it may in answer be urged, 
that the closest examination or most scientific demonstration of 
the chord: vocales and muscles in man, with all the auxiliary 
appendages, afford but an imperfect illustration of the varied 
and extraordi tfiary powers of the human voice. 
EXPLANATION OF THE PLATES. 
Tas. XVII. 
Fig. 1. The glottis in situ. a, a, a. Part of the pharynx. b. The 
rima glottidis. 
2. 2. CE es of the superi r larynx. 
4, à, a. „Cricoid par 
of the trachea. | 
3. b, b. The muscles opening the arytendid: cartilages. 
_a. Part of the muscle closing the arytenoid carti- 
lages. 
4. Shows at a, a, the muscles closing the arytenoid carti- 
lages. 
5. Part of the trachea of a Condor Vulture (Vultur Gry- 
phus). a. Part of the tube, b. Point of divaric Bs. 
adi cis Tite brónchise; arsiz 22 uu = 
`- 6. Side view of the Dier poki n of the trachea of the 
Great Blue and Yellow Macaw (Psittacus Ararauna). 
a. Part of the tube. b. Semilunar bone. c. The - 
bronchia. zl j 
7. Bottom of the tube seen from below, 
VOL. XVI. a Te 
