THE CHANGE IN FJUM 367 



every two seconds until the height of contraction 

 has diminished about one half. Now record the 

 duration of the latent period, phase of rising 

 energy, and phase of sinking energy (page 334) 

 on a rapidly moving drum. 



Note the absolute and relative duration of 

 these periods as compared with those of muscle 

 not fatigued. 



3. Stimulate a sartorius from the same frog 

 continuously with tetanizing currents and record 

 the tetanus curve. 



State the differences between the fatigue curve 

 thus secured and the curve obtained by less fre- 

 quent stimulation. 



Attention has already been called to the dif- 

 ferences which depend on the relative proportion 

 of red and clear fibres (page 336). The latter 

 are more easily fatigued. 



Human Skeletal Muscle. 1. Arrange the ergo- 

 graph to record the contractions of 1 the abductor 

 indicis, as directed on page 353. Place the point 

 of the adjustable rod in the hole nearest the free 

 end of the spring. 



Prepare also the large and small brass elec- 

 trodes for artificial stimulation of the muscle and 

 place them in position. 



Bring the writing point against a very slowly 

 moving drum. Contract the muscle voluntarily 



