STRUCTURES RESEMBLING ORGANIC GROWTHS. 1 73 



ever, the cell-surface resembles the surface of a metallic electrode; 

 local alteration injury, stimulation, chemical change sets up 

 local differences of potential, and currents flow between altered 

 and unaltered regions. The potentials thus arising may be 

 summed, polarizability is marked, and the cell-surface is water- 

 insoluble i. e., there is a sharply denned boundary between 

 protoplasm and surrounding medium. The chief difference in 

 the conditions is that the conduction of electricity both inside 

 and outside of the cell in a bioelectric circuit takes place entirely 

 by means of conductors of the second class, i. e., by ionic move- 

 ment. Both protoplasm and medium are as a rule good electro- 

 lytic conductors; and the surface of separation consists of a 

 thin semi-permeable partition composed of chemically alterable 

 material which is of course non-metallic in character. Can true 

 electrical circuits, in which chemical decompositions of the nature 

 of electrolysis take place at the interfaces, originate under condi- 

 tions of his kind? This question must be considered before 

 the above comparison can be regarded as a valid one and accept- 

 able conclusions be based upon it. 



First of all it is necessary to guard against arbitrary precon- 

 ceptions of the necessary character and arrangement of the 

 different components present in an electrical circuit depending 

 on chemical action, such as we are familiar with in the different 

 types of battery. In all batteries there are at least two contigu- 

 ous conducting media, the one metallic, the other consisting of 

 an electrolyte-solution ; at the boundary-surface between metal 

 and electrolyte chemical changes takes place which furnish the 

 current; the energy of the latter is thus transformed chemical 

 energy. In the usual diagrammatic representation of these con- 

 ditions, the terminals of the one conducting medium, the metal, 

 are regarded as immersed in the other, i. e., the electrolyte; these 

 terminals, where electricity passes between metal and solution, 

 are the electrodes, while the intervening stretch of metal is usually 

 conceived as a wire passing through the air. This last, however, 

 is obviously an arbitrary laboratory arrangement; it facilitates 

 consideration of the processes at either electrode to have each 

 isolated from the other, and the connecting wire removed from 

 the possibility of chemical change; the regions where the essen- 



