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 
Logmeton to sensation. Hence the development 
demands ; a 
: of sense organs different in 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 
box or a padding 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 
Reflex action. 
