CRILE— THEORY OF PROCESSES. 547 



Nernst supposed that the electrolytes in the axis cylinder lie 

 within membranes which are impermeable to certain ions; and that 

 when an electric current is passed through a nerve, it is conveyed 

 by the dissociated electrolytes, causing an accumulation of positive 

 ions at one point and of negative ions at another: when the con- 

 centration reaches a certain point, excitation occurs. A, V. Hill 

 supports Nernst's general theory; and McClendon, Bayliss, Lillie 

 and others take a similar view. Lillie has developed an analogy 

 between the local electrical effects in metals and in living tissue, as 

 exemplified by the passive state in metals and in nerve conduction. 

 He considers that the phenomena in each case are due to the forma- 

 tion of local electrical currents, resulting in the case of metals from 

 local changes in surface tension ; and in nerve tissue from local 

 changes in the permeability of the surface film or membrane. 

 In each case the phenomena are subject to rapid "spreading" as a 

 result of electrical polarization, the rate of " spreading " depending 

 upon the rate of the reaction which initiates it. He states that 

 in nerve tissue " a relation of direct proportion should thus exist be- 

 tween the electric conductivity of the medium and the rate of propa- 

 gation of the excitation wave." 



By microchemical methods MacCallum showed that since it 

 contains a greater concentration of electrolytes, the axis cylinder is 

 a better conductor than the medullary sheath. 



Meyer found that alteration in the concentration of electrolytes 

 in the seawater in which the nerve of a marine animal was sus- 

 pended altered equally the rate of electric conductivity of the water 

 and the rate of nerve conduction. 



Tashiro has demonstrated that as the result of the passage of 

 the normal action current down a nerve fiber, carbon dioxid is 

 given off and oxygen is consumed. He has shown also that when 

 a nerve is stimulated by electricity, the same phenomena are ob- 

 served; i.e., carbon dioxid is given off and oxygen is consumed. 

 jMoreover, whether in the case of the normal or of the eletcrical 

 current, no heat is produced. A. V. Hill has confirmed Tashiro's 

 findings as to the absence of heat; and Benedict was unable to 

 demonstrate heat resulting from mental activity. 



Following the lead offered by the above-cited investigators and by 



