THE PHYSIOLOGY OF THE NERVOUS SYSTEM 221 



4. Observation. (1) Lay the distal end of the cut-off nerve upon 

 the electrode. Stimulate with single-induction shocks of optimum 

 strength. Watch carefully the response of the muscles and repeat 

 the stimulus until the movement is perfectly understood. What is 

 the general movement? 



(2) Palpate the muscles as the stimulation is repeated and deter- 

 mine the individual muscles which respond. 



(3) In what order do the several muscles contract? Is the move- 

 ment due to a single muscle or to several acting together? 



(4) Vary the experiment by tetanizing the muscles. Are any new 

 facts discovered? 



In a similar way any nerve trunk may be stimulated and the 

 response studied. 



