THE EVOLUTION OF THE MIND. 261 



nerve tips which are to move; it is the whole creature. 

 By the division of labour the whole body of the com- 

 pound organism can not be given over 



Locomotion ^^ sensation. Hence the development 



demands . ,.„ . , 



of sense organs dmerent m character: 

 sensation. *» 



one stimulated by waves of light, another 

 by waves of sound ; one sensitive to odour, another 

 to taste ; still others to contact, temperature, muscular 

 strain, and pain. These sense organs must through their 

 nerve fibres report to a sensorium which is distinct from 

 each of them. And in the process of specialization the 

 sensorium itself is subdivided into higher and lower 

 nerve centres ; centres of conscious thought and auto- 

 matic transfer of impulse into motion. This transfer in- 

 dicates the real nature of all forms of nerve action. All 

 are processes of transfer of sensation into movement. 

 The sensorium or brain has no knowledge except such as 

 comes to it from the sense organs through the ingoing 

 or sensory nerves. It has no power to act save by its 

 control of the muscles through the outgoing or motor 

 nerves. The mind has no teacher save the senses ; no 

 servants save the muscles. 



The reflex action then is the type of all mental opera- 

 tions. The brain is hidden in darkness, protected from 



„ ^ . sensation as also from injury by a bony 



Reflex action. , ^ 



box or a paddmg of flesh. It has no 



ideas of its own. It can receive no information direct- 

 ly. But the sense organs flood it with impressions of 

 the external world, and to these impressions the brain 

 chooses corresponding acts. From the body itself, by 

 similar means, are transmitted impressions which be- 

 come impulses to action. Such tendencies in all ani- 

 mals and men are transmitted from generation to gen- 

 eration as a part of the legacy of heredity. They are in 

 their nature rather methods of movement than impulses 

 19 



