SECONDARY MOVEMENTS. 55 



may, on a quiet evening, hear the rabbits answering 

 him all round. These animals, as well as some 

 others, also stamp on the ground when made angry. 

 Porcupines rattle their quills and vibrate their tails 

 when angered; and one behaved 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 continuous sound." 



Secondary movements may be expressive without 

 producing sound. Tossing of the head is often 

 very expressive in a girl; the movement, slight 

 in itself, is rendered more conspicuous by the 

 secondary movements of her long curls. So the 

 horse when neighing shakes his mane, and tosses 

 it in the air movements which express freshness 

 and vigour. A man in prostrating himself on his 

 face bends his body forward by a voluntary move- 

 ment, till the centre of gravity of his body is in 

 front of his base of support, then the body falls, 

 not as the result of a further voluntary effort of 

 movement, but as the consequence of the action 

 of gravity. The first part of this movement is 

 voluntary, and is therefore expressive of volition; 

 the latter part of the movement of prostration is 

 solely the result of gravity. 



Work done is a necessary result of movement of 



