THE ANATOMY OF BIRD-SONG. 121 



"song anatomy," and it must be admitted 

 that it is the highest type of song-bird from 

 every point of view, though its syrinx is ab- 

 solutely insignificant. The anatomy of its 

 larynx is, on the other hand, quite wonderful. 

 For several reasons I have chosen to make a 

 comparison between the shrike and the 

 mocking-bird, mainly, however, on account 

 of the general resemblance borne by the log- 

 gerhead and the mocker in size and coloring, 

 and of the great difference in their voice 

 powers. 



The trachea of the shrike tapers very rap- 

 idly from glottis to syrinx, while that of 

 Mimus is nearly uniform from just in front 

 of the syrinx to where it suddenly expands 

 near the glottidean fissure. The shrike has 

 but three pairs of intrinsic laryngeal mus 

 cles, the lips of the glottis are thick and clum- 

 sy, as compared with those of the mocking- 

 bird, and the fissure is larger and more ob- 

 tusely angular, whilst the tongue is broader 

 and far less delicate than the songster's. 



The laryngeal enlargement of the mocking- 

 bird's trachea is slightly egg-shaped, or keg- 

 shaped ; that of the shrike is simply a con- 

 tinuation of the tracheal expansion beginning 

 at the syrinx. The shrike has a well-devel- 

 oped septum ; indeed, in every particular its 

 syrinx is far superior to that of the mocking- 

 bird, and the contractor muscles of its trachea 

 are much more powerful. Its defect, as in 

 the case of the crow, the cuckoo, and many 

 other birds, lies in the formation of the glot- 

 tis, the mouth-cavity, and the larynx, the 

 shape of the tongue, and the lack of a suffi- 

 cient number of intrinsic laryngeal muscles 

 with which to control the shape and action of 

 the glottidean fissure. 



Viewing the larynx and glottis as the 

 mouth-piece of the avian song-organ or flute, 



