STIMULATION OF MUSCLE AND NERVE 149 



of the galvanic current on nerve. When the 

 irritability of the nerve is raised by drying, weak 

 currents may give opening contractions, although 

 they are absent in normal, uninjured nerves. 

 The interval between the opening of the current 

 and the resulting contraction is then markedly 

 long. In nerves in the first stage of drying the 

 intensity of the nerve impulse (height of cpn- 

 traction of attached muscle) is also more than 

 usually dependent on the duration of the 

 current. 



4. The opening tetanus (so-called Eitter's tet- 

 anus) is probably caused by the rise of irritabil- 

 ity, which takes place in the anodal region when 

 the current is shut off, acting on a nerve already 

 in latent excitation. A similar condition can be 

 produced as follows : 



Smoke a drum. Connect a dry cell through an 

 open key and an electro-magnetic signal with the 

 metre posts of the rheochord (Fig. 41). Connect 

 the zero post and the slider of the rheochord with 

 the pole-changer (with cross-wires), and the latter 

 with two non-polarizable electrodes placed in the 

 moist chamber. Make a nerve-muscle prepara- 

 tion, and secure the femur in the femur clamp 

 of the moist chamber. Attach the muscle to the 

 muscle lever. Bring the writing points of the 

 muscle lever and the electro-magnetic signal 



