BIOELECTRIC PHENOMENA 319 



of the currents produced by the usual combinations of 

 metallic electrodes and electrolyte solutions (or so-called 

 ^'batteries"), with the difference that in the living 

 system the electromotor surfaces consist of thin proto- 

 plasmic films having a composition and structure 

 which are subject to rapid variation. 



The potential changes are relatively small in single 

 cellular elements and their approximate range may be 

 readily determined in parallel-fibered muscles like the 

 frog's sartorius. Here, with a symmetrical side-by-side 

 arrangement of the elements, there can be no summation 

 of potentials; and the conditions are like those of a 

 battery arranged ''in parallel." The maximum range 

 of variation during contraction does not usually appear 

 to exceed 0.05 volt, a potential-difference similar to 

 that of the demarcation-current. According to some 

 observers, however, the potential of the action-current 

 in muscle during strong contraction may be greater 

 than that of the demarcation current, and may even 

 attain 0.08 volt. Comparative observations of the 

 demarcation-current potentials throughout a wide range 

 of invertebrate and vertebrate forms give magnitudes of 

 the order of 0.03 to 0.05 volt.^ The exact physico-chem- 

 ical significance of these values cannot be stated at pres- 

 ent. Bernstein has investigated the influence of temper- 

 ature on the demarcation potential of muscle, and finds 

 that within the physiological range (from 5° to 30°), its 

 magnitude is closely proportional to the absolute temper- 

 ature, as in the case of electrode or diffusion potentials.* 



^ Cf. the data in Garten's article, loc. cit. 



2 Bernstein, Arch. ges. Physiol., XCII (1902), 521, XXXI (1910), 589; 

 cf. also his Elektrobiologie, chap. v. 



