MUSCLE-NERVE. 



(c) Fiftv-per-cent alcohol. 



(d) Glacial acetic acid. 



(e) Five-per-cent sulphuric acid. 

 (/) Ammonia. 



(g) Zinc chloride. 



(h) Allow the nerve to dry. 



4. Electrical Stimuli. For this purpose, induced currents from 

 an inductorium will be used. The effect of the constant current 

 will be taken up later. 



Make a muscle-nerve preparation, arranging for recording upon 

 the smoked drum. Set up the inductorium for single shocks, in- 

 terposing a short-circuiting key in the primary circuit for this pur- 

 pose. Remove the secondary coil, as far as the instrument will 

 allow, from the primary. In those instruments where the secondary 

 is movable to form angles of varying degrees with the primary, the 

 intensity of the secondary currents may be diminished by increas- 

 ing the angle between the primary and secondary wires. 



Apply the electrodes from the secondary coil to the nerve or to 

 the muscle directly. Close the primary circuit. Result ? Record 

 on drum. Rotate the drum slightly and break the primary circuit. 

 Result ? Move the secondary nearer to the primary and repeat the 

 make and break as before, recording results. Repeat again and 

 again, gradually moving the secondary toward the primary until 

 the muscle ceases to increase in the height of its contraction. 

 Which is the more efficacious, the make or the break shock from 

 the inductorium, and why ? 



VII. PERIOD OF LATENT STIMULATION AND FORM 

 OF THE SINGLE TWITCH. 



Arrange a drum to be rapidly spun by hand. With a little prac- 

 tice, this method gives as good results as the pendulum or spring 

 myograph. Arrange a muscle-nerve preparation with point of 

 writing lever touching the smoked surface of the drum. Arrange 

 the writing points of two signal magnets (a) and (ft), exactly under 

 the writing point of the muscle lever. Place signal magnet (a) in 



