Let AB (fig. 1) be a piece of nerve interposed in the galvanometer circuit, and CD in the battery circuit. Then, as has long been known, on closing the battery circuit, one obtains a current in the galvanometer circuit, the direction of which in the nerve is the same as that of the polarising current. If, now, stimulation be made, say at I, this current undergoes a negative variation. Hermann, who investigated the subject, after Bernstein, was at first inclined to explain the negative variation by his law of “polarisation increment.”