S FAMILY CIIARACTEUS. 



ciica above it into the lungs, in a similar manner to \vhicli a 

 reed vibrates in an organ tube. 



All of the shriller and most varied notes are produced by 

 this semiluna membrane. 



Below the division of the broncho trachealis is a long, thin 

 muscle, which, emerging from this point, passes down on 

 either side of the bronichal tubes to terminate on small spurs 

 of the sternum which are pushed out on either side just outside 

 of the junction of the coracoid bones, and which are known as 

 costal processes ( see fig. 4, c). 



The function of the sterno tracheal muscle is to draw down- 

 ward the whole lar^-nx, thus loosening the normally tense 

 tvmpaniform membranes, their vibration then ceases or be- 

 comes muffled, just as the loosening of the strings on a drum 

 muffles the vibration of its head. 



Below the sterno-trachealis is another divided muscle, the 

 bronchialis which extends from the larj'nx to the upper bron- 

 ichal half rings. There are also front and back bronchialis 

 muscles, and to the back of the hindermost is a third division 

 of this muscle known as the short bronchialis. The function of 

 the three divisions of all the 'bronchialis muscles, is to con- 

 tract and draw up the top bones of the bronichal tubes, thus 

 rendering more tense the upper part of the tympaniform mem- 

 branes, producing varying tones, but all of the sounds pro- 

 duced by this membrane are in a minor key. ( ib. o, I, v. ) 



Thus to the adjustment of the three membranes mentioned 

 by the six pairs of muscles described, is due most of the sweet 

 songs of birds, especially in the present family. The effect 

 of the double notes produced by the tympaniform and semiluna 



