VARIOUS TYPES OF RESPONSE 



73 



in muscle-records, in the same circumstances of diminished 

 interval of rest. 



Under certain conditions we obtain an exhibition of 

 continuously growing fatigue. We have seen that when 

 the plant is intensely excited, it takes a longer time for 

 complete protoplasmic recovery. The specimen whose 

 responses are given in fig. 32 happened to be in an optimum 

 condition. A maximum ex- 

 citation was here induced, 

 even under a moderate stimu- 

 lus. The normal interval of 

 15 minutes, which was found 

 in the previous case to be 

 sufficient for complete proto- 

 plasmic recovery, here proved 

 to be insufficient. Hence we 

 have the exhibition of a 

 growing fatigue seen in the 

 diminishing heights of succes- 

 sive responses. 



Another very curious type 

 of response sometimes met 

 with, is that of alternating 

 fatigue. Here, while the first 

 response is very large, the 

 second is correspondingly 

 small, and this alternating 

 sequence is observed for a 

 longer or shorter time (fig. 36) . 

 tions, however, the responses tended to become uniform. 

 An explanation of this interesting variation may be gathered 

 from careful observation of the record. The freshness of 

 the specimen and its high excitability account for the great 

 amplitude of the first response. An intense excitation 

 requires, as we have seen, a correspondingly longer time 

 than does a feeble one for complete recovery. Hence in the 

 present case the second stimulation is seen to have impinged 



Fig. 34. — Fatigue under shortened 

 period of rest. First three 

 uniform responses obtained at 

 intervals of 15 minutes. The 

 second three, under shortened 

 period of rest of 10 minutes, 

 exhibit fatigue. On returning 

 to interval of 15 minutes, the 

 last record shows enhance- 

 ment. 



After several such alterna- 



