42 RESPONSE IN THE LIVING AND NON-LIVING 



previous rest. 



will at once be seen from record D how far the fatigue 

 had been removed. 



One peculiarity that will be noticed in these curves 

 is that, owing to the presence of comparatively little 

 residual strain, the first response of each set is rela- 

 tively large. The succeeding responses are approximately 

 equal where the residual strains are similar. The first 

 response of A shows this because it had had long 

 The first of B shows it because we are 

 there passing for the first 

 time to increased stimula- 

 tion. The first of c does 

 not show it, because there 

 is now a strong residual 

 strain. D again shows it 

 because the strain has been 

 removed by fifteen minutes' 

 rest. 



Fatigue under continuous 

 stimulation. The effect of 

 fatigue is exhibited in 

 marked degree when a 

 tissue is subjected to continuous stimulation. In cases 

 where there is marked fatigue, as for instance in certain 

 muscles, the top of the tetanic curve undergoes rapid 

 decline. A similar effect is obtained also with plants 

 (fig. 24). 



The effect of rest in producing molecular recovery, 

 and hence in the removal of fatigue, is well illustrated 

 in the following set of photographic records (fig. 25). 

 The first shows the curve obtained with a fresh plant. 



FIG. 24. KAPID FATIGUE UNDER CON- 

 TINUOUS STIMULATION IN (a) MUSCLE ; 

 (6) IN LEAF-STALK OF CELERY 



