IX.] PEOPEETIES OF CONTRACTILE TISSUE. 97 



the current is stronger than that caused by 

 making it, a contraction will be obtained earlier 

 on opening than on shutting the primary key. 



0. Tetanus. 



Now arrange the induction machine for an inter- 

 rupted current (§ 4), the secondary coil being at 

 15 or 20 to begin with. 



With the cylinder moving slowly, take a tracing 

 of a tetanic contraction of a muscle, stimulating 

 for not more than three or four seconds. 

 Observe the rise to a maximum at iirst rapid 

 but afterwards more and more slow, the mainte- 

 nance of the maximum during the application of 

 the current, and the fall, at first rapid but after- 

 wards more slow, after the removal of the current. 

 Watch during the tetanus the muscle itself as 

 well as the curve. 



10. Connect one wire from the DanieU's cell with 

 one of the top screws of the primary coil, and 

 the other to the binding screw of the oscillating 

 rod (cp. Appendix), connect a wire with the 

 other top screw of the primary coil and bending 

 the wire place its opposite end in the mercury 

 cup. A key for short-circuiting should be kept 

 in the secondary coil. Allow the full length of 

 the rod to oscillate, open the key in the secon- 

 dary circuit and take a tracing of the muscular 

 contractions ; then take successive tracings with 

 the rod shorter and shorter. 

 Observe the gradual fusing of a series of single 

 contraction curves into the curve of tetanus. 

 L. 7 



