THE PHYSIOLOGY OF THE MUSCULAR SYSTEM 227 



It has been demonstrated that normally the muscle works under 

 the following conditions: (1) contraction with load; (2) relaxation 

 without load or with a very light load; (3) rest without load. This 

 cycle may be repeated for thousands of times in a day; but so long 

 as these conditions are filled the practised muscle can work for three 

 to five hours without fatigue, unless the cycle of changes is too rapidly 

 repeated, or the load abnormally heavy. 



These are some of the problems that may be studied in the field 

 of ergography. 



(1) How much work can be done by the flexors of the third digit 

 of the right hand before fatigue becomes absolute i. e., before 

 fatigue makes it impossible to do more work in any continuous series 

 of contractions. Conditions: load, 5 kilo; rate, 1 every second. 



(2) How much work can be done by same muscle when load is 

 3 kilos? 2 kilos? 



(3) How much work can be done with 5 kilos and rate 1 every 

 half-second ? 



(4) Determine the optimum load and rate. 



1. Appliances. Ergograph or any instrument which fulfils the 

 above conditions (Fig. 85 shows such an instrument); kymograph 

 and tracing apparatus ; metronome to mark the time. 



2. Observation. Adjust the splint to the middle finger and the 

 arm to the arm rest. Fasten the 5-kilo weight to the splint; adjust 

 the tracing apparatus and kymograph in such a way that the con- 

 tractions every two seconds will result in a tracing with a straight 

 abscissa, with lever strokes for the contractions about J mm. apart. 

 Set the metronome to beat seconds. 



Let the subject contract once per second to a moderate extent, and 

 keep it up regularly until fatigued. 



To determine the work done proceed as shown in Lesson XIII., 

 p. 56. 



Use similar technique for various problems, varying only the 

 details. 



