42 FUNCTIONAL INERTIA 



The muscle of so lowly a creature as the lobster 

 behaves under rapid stimulation in an analogous 

 fashion. Fig. 12 shows that a state of tremor 

 sets in almost from the very beginning : its affecta- 

 bility is not equal to keeping pace with the stimuli 

 (28 a second at least), its inertia, its stimulus-disre- 

 garding power is so considerable that it responds 



FIG. 12. First line: record of contractions of muscle of ab lominal 

 somite of lobster stimulated by " tetanising " stimuli (third line) 

 average periodicity 3 per second. Second line : time in half-seconds. 

 (Reduced to two-thirds natural size.) 



only 3 to 6 times per second ; but as fatigue sets in 

 the responses are at such intervals as every 2, 3, 4, 5, 

 or 6 seconds. 



So that in any one neuro-muscular mechanism 

 constant stimuli, instantaneous stimuli, stimuli of 

 relatively high frequency all give rise to the same 

 average periodicity of tremor, new-correspondence is 

 obvious here : affectability alone can hardly be 

 expected to explain it. 



Fatigue is then a state of partial functional 

 disability related not to affectability but to functional 

 inertia set up to avert the onset of exhaustion and 

 death. 



No doubt fatigue is " a chemical affair " ; toxins 



