452 EDWARD HORNE CRAIGIE 



In keeping with this view, several theories as to the funda- 

 mental nature of nervous activity have been propounded. These 

 generally postulate some form of electrolytic action as the es- 

 sential process involved. Macdonald ('05) combines this con- 

 ception with that of a colloidal suspension, about the particles 

 of which the inorganic electrolytes are largely held in a 'masked' 

 condition, from which stimulation causes them to be liberated. 

 Macallum ('12), with experimental evidence in support of his 

 contention similar to that of Macdonald, believes that the funda- 

 mental basis of nervous processes is surface tension. 



Lillie ('18) maintains that a process parallel to nervous con- 

 duction is found in the wave of electrolytic activity which can 

 be produced by similar means at the surface of a passive metal 

 wire immersed in an acid solution. He is inclined "to regard 

 the local bioelectric circuits accompanying normal cell activity 

 as representing primarily some type of oxidation-reduction 

 element," and his description of the process in the metal seems 

 to involve the elimination of a certain, though probably minute, 

 amount of waste matter as the impulse passes along. 



On the other hand, certain experiments of Adrian ('18) suggest 

 strongly that "the energy involved in the passage of the impulse 

 is supplied locally from each point in the fiber through which 

 the impulse passes, just as the explosion wave in a train of gun- 

 powder is maintained by the energy in each part of the gun- 

 powder as the wave reaches it and sets it alight." Johnston 

 COS) has brought forward certain purely anatomical evidence 

 in favor of a similar view. Keith Lucas also supports this view, 

 and after discussing the evidence (up to 1914) as to oxygen 

 consumption and carbon-dioxide production in the nerve fiber, 

 concludes: "However, the whole body of evidence is, I think, 

 sufficient to justify the conclusion that the nerve uses oxygen 

 and gives off carbon dioxide when it is conducting nervous im- 

 pulses" (Lucas, '17). Adrian himself is less positive. He says 

 (loc. cit.), regarding the nervous impulse: "Its nature is unknown, 

 and the only direct accompaniment of it which can be detected 

 with certainty is the electric response. . . . There is pos- 

 sibly an evolution of C0 2 at the same time, but this is still rather 

 doubtful." 



