100 T1IK NKI;\()IS SYSTKM AND ITS COXSKKVATlON 



new route for the application of stimuli. We have very 

 -ati<factory evidence that some of these synapses do fa- 

 tigue, and that an apparent renewal of motor command 

 is secured when new ways of stimulation, involving differ- 

 ent sensory paths, are devised. Let us suppose that our 

 weary traveler suddenly hears martial music. If it is his 

 nature to he moved by the strains we may expect that, 

 for a time, his pace will be quickened and all external 

 sii'ii- of faliirue diminished. 



How shall we interpret the marked effect of the music? 

 There may be more than one opinion as to this, but we 



r. 



I ill. 19. The principle of fatigue in reflex action l-'orbe~' 

 conception. When the reflex obtained through r fails, the action 

 can l>e renewed by shifting stimulation to n. The motor parH 

 are the same in both rases, hence I lie fatigue is in a route of approach 

 to the center. One must, in imagination, multiply all the element- 

 illustrated. 



may indicate a possible explanation alonii the lines of 

 Forbes' experiments. First, we must briefly describe his 

 methods. lie has studied the fatigue of the reflex inech- 

 aiiisni in cats. A nerve containing afferent fillers i- cho-en 

 and its central end is stimulated. ( Vrtain muscles re- 

 spond, and one of these is selected for careful observation. 

 When the stimulation is applied repeatedly the contrac- 

 tions of the muscle are progressively reduced until at 

 length none can be secured. Fatiuue at some point in the 

 apparalu- i< to be inferred, but where'.' The answer is 

 forthcoming when a shift of the electrodes is made to 



