14 



III. Can a Muscle be Stimulated without the Inter- 



vention of the Nerve ? 



Try to answer this question from the results of the last 

 experiment. 



IV. What is the Effect of an Electric Current upon 



Nerve and Muscle? 



A. On the Isolated Nerve-Muscle. 



I. GALVANIC CURRENT. 



Study the galvanic stimulation of nerve and muscle as in 

 I. A, p. 8, using the normal nerve-muscle preparation already 

 made, and increasing the strength of the current by moving 

 the handle on the switch-board from W to S. Record any 

 difference you observe at making and at breaking the 

 current. 



II. INDUCED CURRENT. 



Fit up an induction coil for single induction shocks (p. 9, B) 

 and bring the electrodes upon the gastrocnemius muscle. 

 With the secondary coil well out from the primary, make and 

 break the primary circuit again and again, moving the second- 

 ary coil nearer to the primary between each make and break, 

 and record the result on the muscle, noting each time the 

 position of the secondary coil. 



Repeat the experiment with the electrodes on the sciatic 

 nerve. 



Do the Two Poles act in the same way ? (Galvanic Current.) 



Make a nerve-muscle preparation as described on p. 13. 

 Dip the end of the nerve furthest from the muscle momentarily 

 into boiling water to kill it. It will not now respond to the 

 electric current although it will conduct it. 



Laying the nerve upon a glass slide, place the dead bit of 

 nerve over one electrode, and place the other electrode on 

 the nerve near the muscle. Now make and then break the 



