GENERAL PHYSIOLOGY. 53 



middle to about two-thirds its original diameter, 

 cut it into two such as shown in the figure. Before 

 assembling the parts, that part of the copper wire 

 not covered by zinc, excepting the tip (t) must 

 be painted with brunswick black or any varnish, and 

 the zinc must be amalgamated. With this electrode, 

 as with the preceding, zinc sulphate, kaolin and 

 NaCl 0.6 per cent are used. The part C in these 

 electrodes may be held in a clamp. 

 d. A double myograph. 



A most efficient, as well as convenient and economical 

 double myograph may be arranged for this experiment as 

 indicated in Fig. 10. 



It will be noticed that two common muscle levers such 

 as are shown in Fig. 13, are used, that these are held in 

 position by common clamps and heavy support, that the 

 upper myograph is reversed and its lever counterpoised 

 by the weight (w), that between the two myographs a small 

 wooden block with a longitudinal hole for the loop of 

 thread which holds the muscle is held by a clamp, 

 j. The experiment. 



(1) Curarize a frog. (See Appendix A-5.) 



(2) After the lapse of three hours or more, the sartorius 

 muscle may be prepared as described in Lesson X. 



(3) Mount the preparation by passing a loop of coarse 

 thread through the hole in the block (b), lift the 

 muscle by its tendon of insertion, pass it through the 

 loop, draw the loop gently around the middle of the 

 muscle and fix by making a single knot around the 

 screw (s) of the clamp. The fine hooks which join 

 the muscle to the levers may now be passed through 

 the tendons, and the proper position of the levers 

 effected by an adjustment of the clamps. The non- 

 polarizable electrodes may be clamped between two 



