CHAPTER III 



SENSATION AND REACTION 



BY our senses we maintain some connection with 

 our surroundings. Of the real nature of our 

 environment we are profoundly ignorant ; but it 

 contains our food the material upon which Life 

 exercises its changefulness and to secure this we 

 require not only percipient senses but powers of 

 movement. The necessities of plants are less com- 

 plicated. They feed upon inorganic substances, 

 occurring in the soil, or in the air, which are 

 widely diffused by natural forces, and generally 

 will come if they are waited for. Plants have 

 accordingly cast anchor in the ground, and have 

 lost all but the elements of sensation. Animals 

 must ordinarily seek for their food, whether it 

 consists of vegetable substances or of the bodies 

 of other animals. They have also to avoid the 

 appetites of others. In this matter plants are 

 helpless ; but they have in compensation a power 

 of recuperation which enables herbage, however 

 closely grazed, to restore itself. Animals, further, 

 need senses in order to discover their mates, save 

 in the rare cases when individuals are hermaphro- 

 dite. Moreover, without senses social life would 

 be impossible ; and in the case of many animals, 

 man included, a gregarious impulse has developed 

 itself so strongly that death is hardly worse than 

 to be ignored by others. 



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