NERVOUS SYSTEM. 



IX. To DETERMINE THE NUMBER OF IMPULSES DISCHARGED BY 

 A NERVE CELL IN A GIVEN UNIT OF TIME. 



In an etherized rabbit, adopting the same methods as were em- 

 ployed in the experiment on hemisection of the cord, expose the 

 cord in the middle lumbar region. Insert needle electrodes in the 

 gastrocnemius muscle of one side. Connect these with the capil- 

 lary electrometer. Insert fine needle electrodes through the 

 cord. Stimulate the cord with medium strong single induction 

 shocks at intervals of one second. Is there any response of the 

 gastrocnemius muscle ? If so, what is the nature of this response ? 

 Increase the frequency of stimulation of the cord and note results. 

 Stimulate the cord ten times per second. Does the muscle go into 

 tetanus ? Does the muscular contraction continue after the stimu- 

 lation of the cord has been stopped ? What changes occur in the 

 capillary electrometer ? 



Place the tuning-fork interrupter in circuit with the primary coil 

 of the inductorium. Stimulate the cord again. Does the muscle 

 go into tetanus? What is the frequency of vibration of the me- 

 niscus of the capillary electrometer ? 



Listen with a stethoscope to the muscle during contraction. Is 

 the tone of the tuning-fork reproduced in the muscle? If not, is 

 there any sound heard in connection with the contraction ? 



Compare these results with those obtained when the sciatic nerve 

 was stimulated in the experiment on muscle tone. What is the 

 rate of discharge from the nerve cells in the cord ? 



ESS] 



