214 PHYSIOLOGY AND MORPHOLOGY OF ANIMALS. 



in man. The only difference is that by constant use in 

 modulating the voice in speech and in song the larynx 

 of man is much more flexible. 



Birds.— Next to man, birds have the greatest power 

 of modulating the voice, for many of them sing and 

 some may be taught an imperfect speech. 

 But both the speech and the song of 

 birds have an entirely different signifi- 

 cance from that of man. This, however, 

 belongs to psychology, not physiology.* 

 We should expect, then, that the 

 larynx of birds would be highly devel- 

 oped. On the contrary, it is far inferior 

 to that of mammals (Fig. 136). But the 

 larynx is not the organ of song in birds. 

 The larynx is used only in the simpler 

 and harsher sounds, such as cries of 

 pain, distress, or anger, and perhaps the 

 simple chirp. Their singing organ is an- 

 other organ — the syrinx. 

 Syrinx. — The bird, then, has two organs of voice, the 

 larynx and the syrinx. The larynx is in the usual place 

 at the top of the trachea and opening into the throat ; 

 the syrinx is at the lower end of the trachea. It is made 

 up of the enlarged lower rings of the trachea and upper 

 rings of the two bronchi. Fig. 137, A, B, C, are different 

 views of this organ. Observe (1) that the rings of the 

 bronchi in this part are only a little more than half rings, 

 and the bronchi are completed on the inner side looking 

 toward one another by a tense membrane, which acts as a 

 resonator. (2) On transverse section (Fig. 138) we see 

 transverse floors across the openings of the bronchi into 

 the trachea and a true rima glottidis bounded by vocal 



Fig. 136. — Larynx 

 of a bird. 



* From Animals to Man, Monist, vi, p. 356, 18 



