25 



raises it to near the maximum, and with the muscle stretched 

 by the weight record a contraction. 



B. Now screw up the pin below the lever so as just to 

 prevent the weight stretching the muscle. Adjust the level 

 of the drum so that the lever will be on the same line, and 

 again take a trace over the last on the drum (after loaded 

 muscle). 



Mark the moment of stimulation, etc., as before. Fix and 

 compare the two traces, and work out the extent of contraction 

 and the work done. 



(After taking each trace formulate your CONCLUSIONS as to 

 the effect of the particular condition.} 



VII. What is the Effect of a Rapid Succession of 

 Stimuli ? 



METHODS. 1. With a fast drum, arrange the two strikers 

 on the axle, well apart from one another, and, with breaking 



{ O O $O Q 



FIG. 13. Effect of a Rapid Succession of Stimuli 



1. Induction Coil. 



2. Drum. 



3. Frogboard. 



4. Mercury Key. 



5. Friction Key. 



6. Vibrating Spring with Cup containing 



Mercury. 



7. Gear for producing Slow Rotation of the 



Drum. 



shocks, take a trace of two muscle twitches near the bottom 

 of the drum. Mark the moments of stimulation. Then 

 approximate the strikers so that the second contraction will 

 be produced before the first has ceased, move the drum so 

 that the lever writes at a higher level, and take a trace. 



