20 THE SENSES OF ANIMALS 



unusual for a mammal of even the largest size to shut off its 

 delicate senses when at rest. The constant twitch of the outer 

 ear (when present) will show this to be true, and there is 

 more than a little in the phrase "cat-nap" — watch your own 

 domestic cat and see for yourselves. 



Sight, in the vast majority of mammals, is certainly subor- 

 dinate to smell and hearing ; taste is well developed in many 

 greatly differing species, but it is interesting to note that even 

 the apes, which without doubt have a very fine appreciation 

 of taste, always smell an unfamiliar piece of food before put- 

 ting it into their mouths. 



All mammals have the sense of touch, though not always 

 by means of the parts of their anatomy one would expect. 

 Whiskers, the external nasal processes, and the lips are used 

 where there are no fingers or prehensile toes. 



This brief survey of the most important senses, in some 

 kind of order of priority, will, it is hoped, prepare the student 

 for the more detailed account of the way in which the senses 

 are used by the diverse groups of animals with which we 

 shall deal throughout this book. 



