96 ELEMENTARY PHYSIOLOGY. [iX. 



by the clamp and by the piece of vertebral 

 column, arrange the preparation in the moist 

 chamber as in Fig. 2 Appendix. Load the lever 

 ■with 15 or 20 grammes, and bring the lever 

 to mark on the revolving cylinder. 

 Connect the electrodes with the induction ma- 

 chine arranged for single induction shocks as in 

 §2. 



Set the cylinder rotating at its swiftest speed and 

 with the marker of the secondary coil at 10 take 

 a tracing of the contraction caused by a break in- 

 duction shock (the make shock is prevented 

 from reaching the nerve by shutting the key in 

 the secondary coil, arranged for short circuiting, 

 before that in the primary is shut; on opening 

 in the reverse order the breaking shock passes 

 into the nerve). Observe the rapid but steady 

 rise to a maximum, passing almost immediately 

 into a similar but rather less rapid fall ; the later 

 stages of the fall are distinctly less rapid than 

 the earlier ones. 



Take another tracing over the previous one with 

 the secondary coil at 5 ; the height of the con- 

 traction is somewhat greater. 



8. Place the secondary coil at 25, the key in the 

 secondary circuit being open, shut that in the 

 primary circuit and after a short interval open 

 it; if no contraction follows shift the secondary 

 coil nearer and nearer the primary, stimulating 

 at each shift. 

 Since the induction shock caused by breaking 



