92 



Pa T-ouioJc tc&l 

 ContT-acZton, . 



Fig. 23. 

 Fig. 23, «, nerve ; m, muscle. 



The second branch is stimulated by the electrotonic alter- 

 ation of the first. 



Electrotonus — modification of the vital properties of irrit- 

 able and contractile tissues when influenced by a constant 

 battery current. (Stirling-). 



330. Experiment with Ergogeaph. Adjust the appa- 

 ratus so that the lever will write upon a dwm revolving at its 

 lowest rate of speed. Tie the three fingersof the right hand 

 leaving the index finger free. Adjust this finger to the vertical 

 rod connected with the lever. Raise and lower the finger thus 

 causing a simultaneous movement of the lever, which leaves 

 its record upon the smoked paper. Raise and lower the finger 

 at regular intervals (one second). The abductor indicts is the 

 principal muscle involved. Continue until distinct fatigue 

 occurs. Fix and preserve the tracing. 



XXIV 



331. Elasticity and Extensibility op Muscle. Dis- 

 sect out the gastrocnemius muscle from the frog's leg. Attach 

 the femur firmly in the muscle clamp and the tendon to the 

 writing lever, to which a small scale pan is attached. See 

 that the lever writes horizontally on a stationary drum. The 

 weight of the scale pan may be neglected. 



