Leading off from two places on the same cell (of Nitella) with 0.001 M KCl we observe that a cut produces only a temporary negative current of injury.
If we lead off with 0.001 M KCl from any cell to a neighboring cell we find that when sap comes out from the cut cell and reaches the neighboring intact cell a lasting negative "current of injury" is produced. This depends on the fact that the intact cell is in contact with sap at one point and with 0.001 M KCl at the other (this applies also to tissues composed of small cells).
If we employ 0.1 M KCl in place of 0.001 M the current of injury with a single cell is positive (and is more lasting when a neighboring cell is present).
Divergent results obtained with tissues and single cells may be due in part to these factors.