PRODUCTION OF TETANUS. 



183 



the teeth until a curve unbroken by depressions is obtained. 

 In the curve of complete tetanus the ascent is at first steep, 

 then slightly more gradual, speedily reaching a maximum, 

 when the lever practically records a horizontal line parallel 

 to the abscissa. When the current is shut off the descent is 

 very steep at first, and towards the end very slow. 



Fig. 75. Interrupter for Tetanus. W, Wooden block ; VS, vibrating 

 spring ; BS and BS' , binding screws ; C, movable clamp ; C' , clamp 

 to fix spring ; M, cup of mercury. 



2. Instead of using the spring held in a clamp, a convenient 

 form is shown in Fig. 75. If desired the spring can be kept 

 vibrating by an electro-magnet. 



3. Interruption by a Metronome. Instead of the vibrating rod 

 or Neef s hammer, introduce into the primary circuit a metro- 

 nome, provided with a wire which dips into a mercury cup 

 introduced into the primary circuit. Vary the rate of vibration 

 of the metronome, and observe the effect on the muscle-curve. 



4. Thickening of a Muscle during Contraction. 



(a.) Arrange a Marey's tambour to write on a pendulum 

 myograph (Fig. 76). 



(6.) Fix Marey's pince myographique so as to compress 

 the adductor muscles between the thumb and the metacar- 

 pal bone of the index finger, keeping the two arms together 

 with an elastic band. Or use a pair of toy bellows, to the 



