THE SENSE OF SMELL. 597 



than ideas, this sense plays in man a subordinate part in the acquisi- 

 tion of knowledge. In lower animals this sense is employed for the 

 purpose of discovering and securing food, for detecting enemies and 

 friends, and for sexual purposes. In land animals the entire olfac- 

 tory apparatus is well developed and the sense keen ; in some aquatic 

 animals, as the dolphin, whale, and seal, the apparatus is poorly 

 developed and the sense dull. 



