I am trying to get some background for some personal research I am doing into the effects of Electro Convulsive Therapy. I don't understand how electric current from an external household source, say, flows through the body. There are no naturally occurring chains of metal atoms in the body, so it can't be electron flow, but my understanding is that the electric field around an electrode is very thin, so I can't see ion flow as accounting for electrical effects in the body at some distance from the electode - particularly with AC, as I would only expect a local oscillation. I am familiar with membrane depolarisation but that is essentially a cellular mechanism - is it (or saltatory conduction) activated by an external current? I know that the body as a whole (and cell membranes in particular) function as a dielectric, but I can't see how this fits into the global picture of current flow between two electrodes. Can anyone help or recommend me a paper?