NERVOUS SYSTEM 55 



did not come into the mass. Many were left out for 

 a kind of picket work, and they still acted according 

 to their own will, to some extent, and did not always 

 telegraph to headquarters (literally) for instructions 

 or orders. Nor can the central government always 

 control them wholly. Thus, if the sole of your foot is 

 tickled you jerk it away, and your brain or will has 

 little to do with it ; often can not prevent your foot 

 from jerking. This is ■ because there is a lot of little 

 brains away down there which have very small con- 

 nection with the big brain proper ; and before the 

 latter can have anything to say, the sensation has 

 come to these, and from them the stimulation has gone 

 back — reflected — to the foot. Hence this reflection 

 is called " rejhx action." 



In the movements of the heart and other inside 

 organs, and in the opening and closing of the pupil 

 of the eye, etc., the action is more independent still 

 in answer to outside stimulation. 



The amphibians have a large arrangement of 

 nerve-matter for this purely reflex action — this kind 

 of unconscious work which is not controlled by the 

 brain. 



If a frog's head be cut ofE the body will still be 

 able to move and perform a great many acts which 

 seem intelligent though it will never move of its own 

 will. Something outside of itself must stimulate it. 

 If the skin be pricked here it will scratch the place 

 on this side ; if there, it uses the foot on the other 

 side. If that foot be cut off it uses the opposite foot 

 and stretches it across the body. If the body be 



