86 AN INTRODUCTION TO ZOOLOGY. 



peal' to have any specially prehensile character; but 

 it has been seen to use the tail in this way, and 

 since the mouse often, builds its nest in the stalks of 

 corn, it is easily understood that its climbing powers 

 will thus be greatly assisted. Doubtless the long 

 tails of the mice and rats are put to all sorts of uses ; 

 it is on record that rats have been seen to put their 

 tails down the neck of a bottle of oil, and then lick 

 the oil off; and from this we can understand how 

 easily a mouse can turn its tail to prehensile uses, 

 when there is anything to be gained by doing so. 



The Head. — I forget who it was that first defined 

 the haman being as " a stomach with appendages"; it 

 was an apt description of animal life in any form high 

 enough to possess a stomach. The head may, wiih 

 about as much justice, be defined as a mouth with ap- 

 pendages. The mouth is well at the front of the head; 

 but still more in front (pre-oral) is usually a nose, in 

 some form or other (perhaps very rudimentary, as in 

 Ampldoxua) , to smell whatever presents itself, and 

 judge whether it is fit for the mouth to eat. In 

 insects and crustaceans, the power of smelling is 

 vested in the antennae, or feelers. The eyes are there 

 to see anything at a distance that may be eatable. 

 The ears are useful rather to warn of the approach 

 of something that may eat the owner, than of the ap- 

 proach of something that may be eaten, and the eyes 

 and nose take their share of this office also. 



The mouth itself is a single organ. It is worth 

 while to remark, that the plan of bilateral symmetry 



