TETANUS 563 







While the muscle is entering rigor, move the drum i cm. for each degree, 

 as before, so as to record the development of that process. 



ii. The Form of the Simple Muscle Contraction. Striated muscle 

 responds to electrical stimuli even though of almost instantaneous duration. 

 The response which the muscle gives to a single stimulus is called a simple 

 muscle contraction, and is demonstrated as follows: 



a. Arrange an induction coil with its keys, battery, and electrodes con- 

 nected, so as to stimulate the muscle by the automatic key of the Guthrie 



FIG. 353. Simple Form of Pendulum Myograph and Accessory Parts. A, Pivot upon 

 which pendulum swings; B, catch on lower end of myograph opening the key, C, in its 

 swing; D, a spring-catch which retains myograph, as indicated by dotted lines, and on 

 pressing down the handle of which the pendulum swings along the arc to D on the left of 

 figure, and is caught by its spring. 



apparatus. Set the secondary coil at a position which will give a strong con- 

 traction of the muscle, and record this contraction on the smoked paper of an 

 ordinary recording cylinder. Revolve the drum at a rapid rate using the 

 weight-driven attachment, allowing the automatic key to be opened while the 

 drum is turning at its highest speed. Or use the pendulum myograph, which 

 is especially constructed for this experiment, figure 353. 



b. Make a muscle-nerve preparation with the tendon isolated and the skin 

 removed, Experiment 2, and mount it in a moist chamber, figure 351. Lay 

 the nerve across a pair of platinum electrodes, shake a little water on the 

 inside of the cover of the moist chamber, and place it over the prepa- 

 ration so as to prevent drying of the nerve and of the muscle. 



