OF VITAL PHENOMENA 121 



The H ion concentration of the blood at 20 is about PH = 7.5 

 and with such a reaction outside the cell and PH = 6.5 inside the 

 cell, the theoretical current of injury would be 58 millivolts, which 

 is about the average value actually found. With the model mem- 

 brane given in the first section, the emf did not reach this theo- 

 retical value, but it is reached in the average of one series of 

 determinations by Haber and Klemensiewicz. 



Not only is the cut surface of a muscle negative, but the region 

 of a muscle that is stimulated becomes negative for a fraction 

 of a second. The current produced by this negativity is called 

 the action current, and since the current of injury is produced 

 by the removal of the resistance to diffusion at the cut surface, 

 the action current is probably due to a momentary increase in 

 permeability at the stimulated surface. If this is true we 

 should be able to increase the electric conductivity of muscle 

 momentarily, by stimulating all of the fibers simultaneously. 

 Since it is not easy to measure conductivity in a few 

 thousandths of a second, even with a string galvanometer 

 on stimulating the nerve, another method of stimu- 

 lation was adopted (McClendon, 1912 c). The conductivity 

 of a resting muscle was measured by passing an alternating cur- 

 rent transversely through it. By putting in resistance this cur- 

 rent was made too weak to stimulate the muscle. After the 

 conductivity was determined, the resistance was short circuited 

 and the conductivity determined while the muscle was thrown 

 into tetanus by the alternating current, and found increased 

 from 6 to 28 per cent. It has been objected that the action 

 current of the muscle reinforced the alternating current, but the 

 contrary is true. The muscle is stimulated on the side of the 

 momentary cathode, and the stimulated region, becoming nega- 

 tive, opposes a cathode to a cathode, hence opposes the current. 

 It is also stated that the change in form of the muscle fibres in- 

 creases the cross section of the interfibrillar spaces. This ob- 

 jection seems to have no theoretical basis. If a vessel is filled 

 with small spheres the cross section of the space between the 

 spheres is the same as though it were filled with large spheres. 

 In my experiments a relatively large muscle was pressed between 

 two platinized platinum discs as electrodes. Between the discs 

 were a large number of cylinders (fibers) and when the muscle 



