THE RECORDING OF MUSCULAR CONTRACTIONS 2Q 



tangentially to the curve of the drum with the point of the lever 

 slightly curved in towards the surface of the drum ; (3) the myograph 

 stand, which carries the cork plate and lever upon a vertical rod 

 capable of being turned on its axis, must always be furnished with a 

 stop, so that the point of the lever can always be brought against the 

 drum with exactly the same amount of pressure as that with which it 

 is originally adjusted ; (4) the myograph stand must always be on the 

 right-hand side of the drum, so that the lever extends from right to 



FIG. 33. Muscle-nerve preparation suspended and attached to a straight 

 myograph lever, a, After-loading screw ; b, electrodes. 



left, and the drum itself must always be arranged to move in the 

 direction of the hands of a watch, never in the reverse direction. 



The simple muscle-curve. Arrange the drum in the primary cir- 

 cuit of the induction coil (in the manner shown in Fig. 34), so that, as 

 the drum revolves, a pin (c) which projects from it, by just touching a 

 needle fixed outside, instantaneously makes and breaks the circuit at 

 each revolution. A pair of electrodes is either brought in contact with 

 the muscle itself or the nerve (n) is laid upon the electrodes, which are 

 connected through a short-circuit key with the secondary coil. The 

 secondary coil is placed at such a distance from the primary that the 

 "make" shock is insufficiently strong to act; the "break" shock 



