THE NERVOUS SYSTEM 



401 



ing of the thyroid cartilage, to which one end of the 

 cords is attached. The will cannot influence the con- 

 traction of the vocalizing muscles, except in the very 

 act of vocalization'. The vocal sounds produced by 

 mammals may be distinguished into the ordinary voice, 

 the cry, and the song. The second is the sound made 

 by brutes. The whale, porpoise, armadillo, ant-eater, 

 porcupine, and giraffe are generally silent. The bat's 

 voice is probably the shrillest sound audible 

 to human ears. There is little modulation 

 in brute utterance. The opossum purrs, 

 the sloth and kangaroo moan, the hog 

 grunts or squeals, the tapir whistles, the 

 stag bellows, and the elephant gives a 

 hoarse trumpet sound from its trunk and 

 a deep groan from its throat. All sheep FIG. 356. -Human 

 have a guttural voice ; all the ox family ^J/ a 

 low, from the bison to the musk ox; all f the h yid 



. -Hi bone ; e, trachea ; 



the horses and donkeys neigh ; all the cats /, esophagus; s , 

 miau, from the domestic animal to the lion ; ^s 10 " 15 - 

 all the bears growl ; and all the canine" family fox, 

 wolf, and dog bark and howl. The howling monkeys 

 and gorillas have a large cavity, or sac, in the throat for 

 resonance, enabling them to utter a powerful voice ; and 

 one of the gibbon apes has the remarkable power of emit- 

 ting a complete octave of musical notes. The human 

 voice, taking the male and female together, has a range 

 of nearly four octaves. Man's power of speech, or the 

 utterance of articulate sounds, is due to his intellectual 

 development rather than to any structural difference 

 between him and the apes. Song is produced by the 

 vocal cords, speech by the mouth. 



DODGE'S GEN. ZOOL. 26 



