CONDUCTION IN NERVE 49 



it graphically, take a muscle-nerve preparation with long nerve and attach the 

 muscle to the myograph lever in the usual manner, so that its contractions may 

 be recorded upon a slowly moving drum. Apply stimulating electrodes from 

 the secondary coil to the part of the nerve near the vertebral column, using the 

 Neef's hammer (with Helmholtz wire) for tetanisation. Apply a pair of non- 

 polarisable electrodes connected through a mercury key with a 3-cell Daniell 

 battery, arranged so that the current can be passed up the nerve (polarising 

 circuit). Take a tracing of the tetanised muscle, and whilst this is progressing 

 close the polarising circuit. The tetanus at once ceases, to be renewed on again 

 opening that circuit, and so on repeatedly. 



