PKEFACE vii 



endeavoured to show that this view is erroneous and that 

 both are nourished similarly. 



I have also tried to show that the sensitiveness of the 

 plant and the animal is alike in properties, though differ- 

 ences are apparent in the direction of its differentiation. 



I have avoided as far as possible the discussion of con- 

 troverted points, feeling that this would be out of place in 

 a work intended to serve as an introduction to the subject. 

 Such matters are more properly treated of in the more 

 comprehensive works to which I have already alluded. 



J. KEYNOLDS GREEN. 



CAMBRIDGE. 



