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EXPERIMENTAL PHYSIOLOGY 



effect of fatigue upon the amount of contraction, and also on the 

 extensibility of the muscle both in rest and in contraction. Notice 

 the " staircase " (gradual rise of the ordinates) at the beginning of the 

 curve and the " contracture " (permanent contraction remainder) near 

 its termination. Carry the experiment to complete exhaustion 

 i.e., until the stimuli produce no further perceptible effect through the 

 nerve. Application of the electrodes to the muscle itself will now 

 be found to cause contraction not that the nerve itself is fatigued, 

 but that the junction of nerve and muscle is affected by the fatigue 

 products before the muscle substance itself. 



FIG. 41. Diagram of Mosso's ergograph for the investigation of fatigue in 

 the human subject. 



Recovery. Allow the preparation to rest, keeping it moist with 

 Ringer's solution. After 15 or 20 minutes again test the effect 

 of a stimulus. Notice that there is a certain amount of recovery from 

 the fatigue, even in a preparation such as this in which no blood 

 is circulating. In muscle in which the circulation is maintained 

 fatigue not only comes on more slowly but is more rapidly recovered 

 from, since the circulating blood removes the fatigue products. 



Reaction of the fatigued muscle. Cut across a muscle which is 

 completely fatigued, and apply blue litmus paper to it. Notice that 

 the paper is reddened (production of acid fatigue products). Compare 

 the reaction with that of a piece of fresh, unfatigued muscle. Muscle 



