THE NERVOUS SYSTEM 225 



QUESTIONS 



1. How is irritability related to being alive in the case of a plant ? 



2. What is there in a one-celled animal that corresponds to our 

 nervous system? 



3. What useful movements does your body perform without the con- 

 trol of your purpose ? 



4. What other useful adjustments or responses does your body make 

 without the control of your purposes ? 



5. What advantages would there be in being able to control these 

 movements and processes ? What disadvantages ? 



6. What automatic movements are performed in your body that are 

 useless or possibly injurious ? 



7. What automatic movements would it be desirable to control ? 



8. What automatic movements can we learn to control ? 



9. How can we tell that reflexes depend upon nerve connections ? 



10. How can we tell that some nerves carry only afferent disturbances 

 and others only efferent disturbances ? 



11. Under what conditions is it of advantage to an organism to be 

 sensitive to what is happening ? 



12. Under what conditions is it disadvantageous to be sensitive ? 



13. What reflexes seem to be of no use to the body ? 



14. What becomes of nervous energy that is discharged by a stimulus 

 when there is no outward movement ? How can you tell in such cases 

 that something really happens in the body, even if it does not show on 

 the outside ? 



15. Of what value is it to the organism to be able to defer or postpone 

 its reaction or to prevent an immediate reaction ? 



REFERENCE READINGS 



Hough and Sedgwick. The Human Mechanism, chap, vii, The Adjust- 

 ment, or Coordination, of the Work of Organs and Cells; chap, xv, 

 The Nervous System. 



Parker, G. H. Biology and Social Problems, lecture on The Nervous 



System. 



