426 SINGING PERCIIER& 



ORDER OSCIMES, SINGING PERCHERS. 



Difler from the soiigless IVrchcrs in hiiring the back portion of the tarsi pro(Uice(l in- 

 to a sharpened ridge asseen in B in the figure given on page 401. (There are some except- 

 ions to tliis rule, among which are the Horned Larks. These do not have the sharpened 

 ridge. )x\lso in havmgsix distinct pairs of inferior larvngenl musele-J, and tl:e sterno-tra.che- 

 ahs has its origin between the (hvlsions of tlie l)roncho-trachealis anticus and poi-ticiis. 



I have o;iven a hfe-sizA'il (hawing of i\\v inferior larynx of a Criw in Plate XXXIII, 

 tigs. 1 to 4, in order that students may understand the various parts. Fig. 4 shows a view 

 from tlie lower side ; 0, is aportion of the trachea and B, the bronchial tubes which extend 

 to the lungs. Tlie muscles which are deeper in color, are as follows: Bt, bronclio-traclie- 

 alis; Bp, broncho-trachealis posticus. Fig. 3 exhibits a side view with the sa.me iigiu'es 

 applied to the same parts as far as explained. The broncho-trachealis is better defined and 

 its division into the broncho-trachealis anticus, B, and posticus, Bp, is very clearly seen. 

 The broncho-tracheahs brevis is given at Bl), the bronchiidis posticus at BB, wliich with 

 the bronchialis anticus, BBa make up the numl^er of vocal nmscles ; their counterparts 

 being on the opposite side. It is observable that the sterno-trachealis has its traclieal or- 

 igin below the division of the broncho-trachealis; the other extremity being attached to 

 the costal process of the sternum, seen in fig. 5, Cp. 



The other accessories for jiroducing melodious sounds are the tympaniform membrane 

 which stretches across the under side of the upper portion of the l)ronchial tul)es, fig. 2, 

 M, and the semilunar membrane, shown in fig. 1, which is a section of the larynx, at 8. It 

 is supported by the OS transversale, T, a slender bone w hich crosses the interior of the tra- 

 chea. The office of the laryngeal muscles is to tighten these two rnendjranes, which then 

 ■vibrate and produce sounds. 



