5*8 



MUSCLE-NERVE PHYSIOLOGY 



stimulus which produces a maximal contraction is called the maximal stimu- 

 lus, and all stronger stimuli supramaximal. 



7. The Effect of Fatigue on the Amplitude of a Series of Simple 

 Muscle Contractions. Prepare a gastrocnemius muscle for direct stimula- 

 tion and mount it in a moist chamber. Arrange the induction apparatus for 

 single stimuli. Adjust the recording lever of the muscle to a smoked-paper 



FIG. 353. Record of a Simple Contraction of the Gastrocnemius of the Frog. Time 

 in .01 of a second. St, Moment of stimulation. Record taken on a rapid drum that was 

 provided with an automatic key. 



kymograph and set the speed of the kymograph to revolve at the rate of i mm. 

 per second. Now stimulate the muscle with the make induction (short- 

 circuiting the break) once every two seconds. The contractions will be re- 

 corded as vertical marks on the drum in regular order, at a distance of 2 mm. 

 apart, hence very slight changes in amplitude are readily detected. The 

 contractions gradually increase in height for the first ten or twenty, the phe- 



FiG. 354. The Type of Contractions given by the Gastrocnemius of the Frog to a 

 series of stimuli occurring at regular recurrent intervals. (Taskinen.) 



nomenon of treppe, then run for from fifty to one hundred contractions of 

 practically uniform amplitude, after which there is a gradual but sharp 

 decrease known as fatigue. Repeat the experiment after ten minutes' rest. 

 The former variations occur now very rapidly, indicating that the fatigue 

 effects are only partially recovered from. 



8. The Effect of Fatigue on the Time of the Simple Contraction. 

 Prepare a muscle nerve and mount it in the moist chamber, arrange for the 



