CHAPTER V 

 REFLEX ACTION 



IN the previous chapter it was pointed out that all the 

 work done by the skeletal muscles is in response to the 

 discharges of the central nervous system. For the other 

 types of muscle the cardiac and the visceral it was 

 shown that there is an inherent tendency to rhythmic 

 activity, but that over these tissues also the nervous sys- 

 tem exercises a regulation. Finally, it was stated that the 

 glands likewise are subject to central government, al- 

 though not to the same degree in all cases. We must 

 now proceed to consider how the nerve-centers are them- 

 selves prompted to throw muscles and glands into action. 



As we observe the body at work we cannot fail to be 

 impressed with the timeliness of its adjustments. It is 

 constantly meeting with emergencies and adapting itself 

 to new conditions. If we are inclined to attribute all 

 these quick adaptations to intelligent choice of courses 

 to be pursued we shall find that we cannot long defend 

 such an explanation of the facts as they occur. We can- 

 not pretend that we think of each inequality of the 

 pavement as we cross the street, or of each individual in 

 the crowd through which we make our way. The balan- 

 cing of our bodies, standing or walking, is not a matter 

 about which we are given to deliberating. These things 

 seem to take care of themselves. It is such adjustments 

 which " seem to take care of themselves " that are called 

 reflex actions. A reflex is an adaptive change to meet 

 some new external condition brought about through the 

 agency of the central nervous system. We may or may 

 not notice the occurrence of a reflex. If consciousness 

 is at all involved, it is incidental and not causal. Often 



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