XLIII.] MUSCLE WAVE. 22? 



a recording crank-myograph. Arrange time marking apparatus 



(b.) Dissect off with great care the sartorius of a curarised frog 

 (p. 1 86), and connect its tibial end with the myograph-lever. 



(c.) Clamp the muscle a little to the tibial side of the middle 

 line in a cork clamp, made by pushing two pins parallel to each 

 other through two thin pieces of cork ; the points of the pins project 

 and serve to fix the preparation on the cork plate of the myograph 



(%. 149). " 



(d.} Thrust two pins through the muscle close to the clamp 

 and two near its free end. These act as electrodes and are con- 

 nected with the thin wires from the commutator, so that the muscle 

 can be stimulated either near the clamp or far away from it. 

 Stimulate the muscle first near the clamp and record the contraction, 

 reverse the commutator, excite it away from the clamp and record. 

 Two curves, one rising later than the other. The distance between 

 the two indicates the time taken by the wave of contraction to pass 



FIG. 149. Arrangement for study of Muscle Wave. E, E'. Pin electrodes ; C. Cork 

 clamp ; L. Lever. 



over the distance from the far to the near electrodes. Measure the 

 distance between the electrodes and calculate its velocity. It varies 

 from i to 2 metres per second. 



(e.) Test the effect of cold normal saline in slowing its rate. 



2. (a.) Arrange two long straw levers on a cork frog-plate so 

 that the two free ends of the levers record exactly over each other 

 on a revolving drum. Record time (-j-oV). 



(/>.) Remove the double semi-membranosus and gracilis (p. 179) of 

 the thigh from a curariscd frog, together with their bony attachments, 

 and place them under the levers, the levers lying across them, and 

 as far apart as possible. Let the muscles rest on paraffined paper. 

 Fix the muscles through their bony attachments by means of pins. 

 Through one end of the muscles push two pins attached to wires to 

 act as electrodes. Some prefer the two sartorii muscles, fastened 

 together, the one lying on the other and fixed by means of pins. 



(e.) Stimulate with a maximal break induction shock and note 

 that two curves on different abscissae are obtained, the one a little 



