VOCAL ORGAN OF BIRDS. 



223 



103, b, making a prominence where the external vocal fold is 



continued over it, in the starling, thrush, nightingale, &c., has 



been called ' arytenoid cartilage,' from its analogy to that of the 



upper larynx of Mammals. The proper muscles of the lower 



larynx, as seen in the Raven, 



are shown in fig. 104, in front ^'^'^ 



view A, and side view B. 



The muscle answering to 

 the ^ tracheo-lateralis ' in Vo- 

 litores expands toward the 

 lower end of the trachea and 

 divides into two fasciculi 

 which diverge, the one, f, to 

 the fore, the other, a, to the 

 back part of the bronchus, to 

 be inserted into the corre- 

 sponding extremities of the 

 third half-ring, fig. 104, c. 

 The fasciculus, fig. 104, b,/, is 

 the * broncho-trachealis anti- 

 cus : ' the fasciculus, a, is the broncho-trachealis posticus. Beneath 

 this is a shorter muscle, ib. b, the broncho-trachealis brevis, which 

 is inserted into the posterior end of the second bronchial half- 



A front, B side, view of lower larynx. Raven, xxx*. 



The remaining two muscles are enlarged divisions or differen- 

 tiated fasciculi of the common laryngeal muscle (Kehlkopfmuskel, 

 Miiller^) of Volitores: the ^ bronchialis posticus,' ib. c, arising 

 from the lower and lateral border of the last tracheal ring, swells 

 into a ^ venter,' and contracts as it passes backward to be inserted 

 into the hinder end of the second half-ring. The ' bronchialis 

 anticus,' ib. e, is partly covered by the ^ broncho-trachealis anticus,' 

 and is thick and ventricose : it arises from the last tracheal ring; 

 and passes forward to its insertion into the fore ends of the first 

 and second half-rings and into the supplemental (arytenoid) car- 

 tilage. 



All the foregoing muscles tend to tighten the whole or parts of 

 the tympaniform membrane which is below their points of inser- 

 tion, and to relax the part above the insertion. They lengthen 

 the part of the bronchus below or beyond their insertion and 

 shorten the part above, by approximating to the trachea the half- 

 rings they are attached to. The chief antagonistic power is the 



