Mr. Yarrell 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 chordae vocales and muscles in man, with all the auxiliary 

 appendages, afford but an imperfect illustration of the varied 

 and extraordinary powers of the human voice. 



EXPLANATION OF THE, PLATES. 



Tab. XVIL 



Fig. 1. The glottis in situ, a, a, a. Part of the pharynx, b. The 

 rima glottidis. 



2. Cartilages of the superior larynx, a, a, a. Cricoid car- 



tilage, b, b. Arytenoid cartilages, c. Upper rings 

 of the trachea. 



3. 6, b. The muscles opening the arytenoid 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. 6. Point of divarication, 

 c, c. The bronchiae. 



6. Side view of the lower portion of the trachea of the 



Great Blue and Yellow Macaw (Psittacus Ararauna). 

 a. Part of the tube. b. Semilunar bone. c. The 

 bronchia. 

 7- Bottom of the tube seen from below. 

 VOL. XVI. 2 T Fig. 



