64 



EXPERIMENTAL PHYSIOLOGY 



joining the lower, and in addition one other feature is observed, viz 

 that the amount of contraction progressively increases throughout. 



In these last four curves it is to be noticed that the relaxations of 

 the first few contractions progressively increase. In curve 5, for 

 instance, the first relaxation is practicaily nil, the second 2 mm., the 

 third 3 mm., the fourth 3 mm., and at a later stage when fatigue 

 begins to set in, they again diminish in amount, due to the cause 

 already explained. The meaning of this increase in relaxation 

 receives a certain degree of explanation in the light of the fact already 



Fig. 63.— The Genesis of Tetanus with slow Rotation of Recording Surface. 



studied, that the apex time of the second twitch in a summation 

 series is less than that of the first. The diminution of apex time in a 

 series has also been found to extend to the third, and in favourable 

 cases to a fourth or later contraction. 



In the last curve (7) a practically complete tetanus is recorded 

 which was produced when the rate had reached thirty per second. It 

 is seen that the upper line of the whole curve very gradually ascends. 

 There are slight wavy oscillations on this fine, which, however, are 

 not synchronous with the series of stimuli. 



