ON SOME PHYSICAL MANIFESTATIONS OF LIFE 69 



if in an active or injured element of the nerve or muscle acid is formed, 

 the hydrogen-ions must migrate faster into the neighboring tissue than 

 the anions. Consequently, the active element will have an excess of 

 free negatively charged ions, while the neighboring resting elements wiU 

 assume a positive charge (Fig. 14). I pubKshed this explanation of the 

 origin of currents of action in a preliminary way in an address at the 

 Naturalists' meeting in 1897.* Oker-Blom-j- has since expressed a 

 similar view in regard to the current of demarcation; and he mentions 

 that Tschagovetz has published a similar view in a Russian journal. 



Ostwald } has pointed out that the semipermeable membranes may 

 possibly be permeable for only one class of ions, positive or negative, 

 and "not only the currents in muscles and nerves, but also the myste- 

 rious effects of electrical fishes might find their explanation by such 

 a property of the semipermeable membranes." Bernstein § and Briin- 

 ings II have recently adopted this view. Bernstein pointed out that, 

 in order to explain the above-mentioned current of action, a specific 

 permeabiUty of the semipermeable membranes for cations must be 

 assumed. It is hardly possible that differences in electrical poten- 

 tial can arise in any other way in the tissues than by a separation of 

 anions and cations of the electrolytes dissolved in the tissues. As 

 the difference in the rate of diffusion for different ions always exists, 

 especially when acids or alkalies are formed, and as a difference of the 

 permeabihty of the protoplasm for oppositely charged ions inay also 

 easily exist or arise, it is not difficult to understand that so many hfe 

 phenomena are accompanied by electrical changes and currents, e.g. 

 when light falls upon the retina, or when glands secrete. 



Plants also show such currents, especially such plants, as are dis- 

 tinguished by a comparatively quick conduction of stimuh, e.g. Mimosa 

 or Drosera. This lends, perhaps, support to the idea expressed by 

 Hermann that the current of action is the cause, or means, of the propa- 

 gation of the nerve impulse. When a nerve or muscle is stimulated, 

 the stimulated spot becomes negatively electrical as compared with 

 the neighboring resting spot. In the next element of time this latter 

 spot becomes the seat of activity, and now becomes negative toward 

 the more distantly situated piece of nerve, etc. A region or wave of 

 negative potential is thus propagated from the original seat of stimu- 

 lation in both directions, through the nerve. Bernstein has found 

 that this negative wave is propagated with the same velocity as the 



• Loeb, Science, N. S., Vol. 7, p. 154, 1898. 

 t Oker-Blom, Pfiuger's Archiv, Vol. 84, p. 191, 1901. 

 X Ostwald, Zeitsch. fur physik. Chemie, Vol. 6, 1890. 

 § Bernstein, Pfiuger's Archiv, Vol. 92, p. 521, 1901. 

 II Brunings, Pfiuger's Archiv, Vol. 100, p. 367, 1903. 



