LABORATORY MANUAL OF PHYSIOLOGY. 



volve slowly. Attach the muscle to the myograph lever. After- 

 load with a lo-gram weight. Adjust lever to drum. Stimulate the 

 nerve once a second with a submaximal induction shock. 



A fatigue record formed of single twitches, written one after the 

 other, will thus be obtained. 



3. Repeat the above fatigue experiment with a loaded muscle. 



XIII. VOLUME OF CONTRACTING MUSCLE. 



In answer to the question, does the volume of the muscle change 

 during contraction, some such device as that shown in Fig. 12 

 may be used. The muscle should be put in a container filled with 



physiological salt solution, the ends 

 of the muscle being attached to elec- 

 trodes from the secondary coil of an 

 inductorium arranged for tetanizing 

 shocks. The mouth of the container 

 is closed with a tightly fitting cork, 

 perforated for the passage of a fine 

 glass tube in which the water from 

 the container rises. 



Stimulate the muscle with tetaniz- 

 ing induction shocks and observe the 

 level of the fluid in the capillary tube 

 connected with the muscle container. 

 Does the fluid rise or fall ? Does the 

 volume of the muscle change during 

 contraction ? 



XIV. SUMMATION OF STIMULI. 



FIG. 12. To Determine Volume 

 of Contracting Muscle. Af, Mus- 

 cle ; e e, electrodes ; c, capillary 



Arrange inductorium with second- 

 ary coil removed from primary until single break shocks are just 

 insufficient to cause a muscle twitch. Let the muscle rest for 

 several minutes. Now stimulate the nerve every four or five 

 seconds. Does the muscle finally contract ? Explain. 



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