GENERAL PHYSIOLOGY. 55 



will record on the drum the time of making stimulus and 

 the time of breaking stimulus. The recording point of 

 the time marker should, of course, be in the same vertical 

 line with the myograph points. The moist tips of the 

 N-P electrodes should be so adjusted as to just touch the 

 muscle above and below the loops of thread. 



(1) Close the key. If the preparation has been sue 

 cessful, the half of the muscle in contact with the 

 kathode pole will respond before the other one. 



(2) Break the current. The anode should respond first. 



(3) Reverse direction of current and repeat (1) and (2). 



(4) Vary the strength of current through use of simple 

 rheocord and determine whether the results are the 

 same for currents of different strength. 



Law I. The make-contraction starts at the kathode and the 

 break-contraction starts at the anode, or 

 When irritable tissue, muscle, or nerve, is subjected to a 

 galvanic current the response to the stimulation begins in 

 the region of the kathode on making the current and in 

 the region of the anode on breaking the current. 



Would the foregoing observations justify the following 

 statements: (1) Kathcdic contractions, or make contrac- 

 tions, may be caused by a galvanic current which is too 

 weak to cause anodic contractions or break contraction. 

 (2) Kathodic or make contractions are stronger than 

 anodic or break contractions. 



