70 DYNAMICS OF LIVING MATTER 



nerve impulse, so that there exists a possibility that this difference of 

 potential which originates upon stimulation is the cause, or the means, 

 of propagation for the nerve impulse. Hermann has given a more 

 detailed sketch of such an assumption.* The axis cylinder of the 

 nerve is surrounded by a liquid conductor of electricity, i.e. a solution of 

 electrolytes. If a certain element A of the axis cylinder be stimulated, 

 it will assume a negative charge, while the neighboring parts B assume 

 a positive charge. This leads to the formation of a microscopic cur- 

 rent from B through the liquid conductor to A. This current may 

 be considered as a stimulating current for the axis cylinder with an 

 anode at A and a cathode at B. We shall see in a later lecture that 

 if a current be made, the stimulation occurs at the cathode, while the 

 anode is put into a condition of diminished irritability. Therefore, 

 the region A now returns to a condition of rest, while B becomes active. 

 Then the same process is repeated for B and its neighboring element, etc. 

 Waller has been able to determine the beginning of life in the hen's 

 egg and in seeds of plants by galvanometric tests; he has also deter- 

 mined the cessation of life in the same manner. f These facts may 

 serve as a further indication that all life phenomena are accompanied 

 by electrical phenomena. We shall see later that salts play a great 

 role in life phenomena ; and it is obvious that if changes in the nature 

 and number of ions in a solution accompany life phenomena, electrical 

 currents must also be a necessary consequence. 



* Hermann, Handbuch der Physiologie, Vol. 2, 1st part, p. 193, 1879. 

 t Waller, C. R. de r Academic des Sciences, Vol. 131, pp. 485 and 1173, 1900. Proceed- 

 ings of the Royal Society, Vol. 68, p. 79, 1901. 



