VARIOUS TYPES OF RESPONSE 



n 



same improvement of tone might take the form of a 

 gradually increasing excitability. Hence the gradual better- 

 ing the tonic condition, under successive stimulations, may 

 often rind two simultaneous expressions. In the first 

 place the growing tone, with its increasing normal tonic 

 contraction, will be seen in the shifting of the base-line 

 upwards. Secondly, it will be exhibited in the growing 

 amplitude of successive responses. These two features will 



Fig. 37. — Preliminary staircase 

 followed by fatigue in the 

 response of frog's muscle. 

 (Brodie.) 



Fig. 38. — Staircase response 

 followed by fatigue in 

 Mimosa. 



both be noticed in the record depicted in fig. 38. Here, 

 as might be expected, in a specimen in sub-tonic condition 

 we find that the first stimulus gives rise to a relatively feeble 

 response. But in consequence of stimulation the tonic 

 condition itself is improved, as demonstrated by the fact 

 that the leaf remains in a slightly more contracted attitude 

 than at the beginning. The next stimulus finds it in a 

 better tonic condition, with accompanying higher excita- 

 bility. Hence the response is larger. In this way the tonic 



