466 MANUAL OF PHYSIOLOGY. 



for tetanic action are accomplished by the interposition, at a cer- 

 tain moment, of the action of an antagonistic muscle which stops 

 the movement an<l makes the act extremely rapid. 



With from twenty a second to upwards of many hundreds of 



FIG. 101. 



Curve ot tetanus resulting from 30 stimulations per second, drawn on a 

 drum rotating slowly compared with the motion of the Pendulum Hyograph. 

 The stimulation commences at "30," and ceases just before the lever begins 

 to fall. No trace of the individual contractions of which the tetanus is 

 composed can be recognized. 



induced shocks one can produce tetanus in a frog's muscle. The 

 lowest, limit of this range is probably about the number of im- 

 pulses communicated to human muscles by their nerves, since the 

 tone produced by contracting muscle corresponds to the first over- 



FIG. 192. 



Curve of tetanus composed of imperfectly fused contractions resulting 

 from 12 stimulations per second. The serrations on the left of the curve in- 

 dicate the individual contractions. 



tone of a primary note produced by 19.5 vibrations in a second. 

 The number of stimuli required varies with the rate of contrac- 

 tion of the muscle employed, the quick contracting bird's muscle 

 requiring 70 per second, while the exceptionally slow-moving 

 tortoise muscle only requires 3 per second. According to some, 



