ELECTRIC CURRENTS OF MUSCLE 51 



Expose the gracilis of the opposite side and stimulate 

 different points on one side of the tendinous insertion 

 with weak faradic currents; the ends of the electrodes 

 being close together. At some points contraction will 

 be obtained on the opposite side of the tendinous in- 

 sertion, at others on the same side only. 



Similar experiments may be made on the rectus abdominis and 

 sub-maxillary muscles of the frog. In the former, salt placed on 

 one segment causes great shrinking of the segment and some twitch- 

 ing in the segment above or below or in both. In the latter there 

 are no segments, but the branching of the nerve fibres is greater 

 than in the skeletal muscle, and salt placed on the anterior part will 

 cause twitching in the posterior part. 



3. Stimulation by the injury (demarcation) cur- 

 rent and by the current of action. (Rheoscopic 

 frog.) Arrange a coil for single induction shocks. Re- 

 move the skin from the legs of the frog and dissect out 

 both sciatic nerves from the vertebral column to the 

 knee. Suck up with blotting paper any blood or lymph 

 from the legs and place the frog on a clean dry cork 

 board. With a scalpel make a transverse incision into 

 the extensor muscles of one thigh, e.g. the left, just 

 above the tendons. Cut off the end of the left sciatic 

 near its origin. With a glass rod lift up the nerve, and 

 let it fall across the thigh muscles so as to come in con- 

 tact with the surface and the cut end. As the nerve 

 makes contact, a contraction of the muscles supplied 

 by it will occur. The injury current of the thigh muscles 

 stimulates the nerve. Divide the Achilles tendon of 

 the right gastrocnemius, fix the tendon by a pin close 

 to the left knee, and, taking care not to injure the 

 right sciatic, fix the right knee with a pin. Raise the 



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