THE CHANGE IN FORM 353 



An isometric contraction will be recorded. 



Remove the spring, and attach the tendon to 

 the lever weighted with ten grams. Stimulate 

 the muscle with a break induction current of the 

 strength used before. 



The usual isotonic curve will be written. 

 Comparison of the isometric and isotonic curves 

 reveals as a rule in the isometric curve a longer 

 phase of rising energy and a flattened summit 

 or plateau. The muscle reaches its maximum 

 tension sooner than its maximum shortening and 

 maintains the maximum tension longer than the 

 maximum shortening. 



CONTRACTION OF HUMAN MUSCLE 



Simple Contraction or Twitch. Place the 

 middle, ring, and little fingers in the support of 

 the ergograph (Fig. 61). Let the adjustable rod 

 rest on the index finger near the distal end of 

 the middle phalanx. Place the point of the rod 

 in the hole nearest the free end of the spring. 

 Adjust the writing point to write on a smoked 

 drum revolving at moderate speed. With the brass 

 electrodes covered with wet cotton (page 129), 

 stimulate the abductor indicis with a single max- 

 imal break induction current. Compare the form 

 of the curve thus obtained with the contraction 

 curve of the skeletal muscle of the frog. 

 23 



