Chap. IV. 



IN ANIMALS. 



93 



the tittering of monkeys should be a rapidly reiterated 

 sound, cannot be explained. During the utterance of 

 these sounds, the mouth is transversely elongated by 

 the corners being drawn backwards and upwards; and 

 of this fact an explanation will be attempted in a future 

 chapter. But the whole subject of the differences of 

 the sounds produced under different 

 states of the mind is so obscure, that 

 I have succeeded in throwing hardly 

 any light on it; and the remarks which 

 I have made, have but little signifi- 

 cance. 



All the sounds hitherto noticed de- 

 pend on the respiratory organs; but 

 sounds produced by wholly different 

 means are likewise expressive. Bab- 

 bits stamp loudly on the ground as a 

 signal to their comrades; and if a man 

 knows how to do so properly, he may 

 on a quiet evening hear the rabbits 

 answering him all around. These ani- 

 mals, as well as some others, also stamp 

 on the ground when made angry. Por- 

 cupines rattle their quills and vibrate 

 their tails when angered; and one be- 

 haved in this manner when a live snake 

 was placed in its compartment. The 

 quills on the tail are very different from those on the 

 body: they are short, hollow, thin like a goose-quill, 

 with their ends transversely truncated, so that they are 

 open; they are supported on long, thin, elastic foot- 

 stalks. Now, when the tail is rapidly shaken, these 

 hollow quills strike against each other and produce, 

 as I heard in the presence of Mr. Bartlett, a peculiar 



Fig. 11. — Sound -pro- 

 ducing- quills from the 

 tail of the Porcupine. 



