Demarcation Current in Frog's Sartorius. 143 



Na ions. This action is reversible. The author has repeated 

 Overton's experiments and in addition to confirming them found 

 that the relation of K in the muscle cell bathing fluid to the 

 potential developed by injury of the muscle is a quantitative one 

 and also that it is possible to get not only a change of direction 

 for the demarcation current by replacing Na in the cell bathing 

 fluid by sufficient K but also to get a pseudo action current under 

 these circumstances. This pseudo action current only travels a 

 short distance along the muscle, is of slow rate of progression and 

 is accompanied by a small, slow contraction. 



From the above experiments it was concluded that a displace- 

 ment of K ions across a semi-permeable cell boundary was respon- 

 sible for the demarcation current of muscle. At the moment of 

 cutting or injuring a muscle cell there is opportunity for ion 

 equilibrium at the cut surface, whereas there is ion and thus 

 electric strain at the uncut surface. If this hypothesis is true 

 the velocity with which the demarcation current develops to its 

 maximum intensity is of the order of 1/100,000 of seconds because 

 of the speed of ions and the distance to be travelled by them. 

 Garten has cut the surface of the frog's sartorius and determined 

 the speed with which the demarcation current rises to its maxirmim 

 value by means of the capillary electrometer. He believes that 

 his experiments show that more than 1 / i ,000 of second is necessary 

 for the demarcation current to develop. 



The analysis of Garten's capillary electrometer curves is based 

 on the formula D(ds/dt) + Ks = Ci. This formula neglects the 

 mass factor because usually the mass is so small in relation to the 

 friction that it may be neglected. 



M T? + D 7t + Ks = ci 



is the equation which accurately describes the forces acting on 

 the capillary when a potential difference is applied to it. 



Curves analyzed according to the first formula do not give an 

 accurate picture of the development of potential difference during 

 the first 1/1,000 of a second. Therefore we do not believe that 

 Garten has proved that it takes more than 1/1,000 of a second to 

 fully establish the current of injury- of a frog's muscle. 



