That different tissues produce a varying resistance to the passage of an electric current has long been known. Waterman,1Crile2and others have tested out the electrical conductivity of tissues and shown that there is a difference in conductivity between normal and fatigued tissue and between healthy and pathologic tissue. Meyer and Schlueter3used the degree of resistance of the brain tissue to an electric current as a means of differentiating between normal brain and tumor tissue at the operating table. It is this application of the resistance of tissue to the passage of an electric current that is of particular interest. Meyer and Schlueter report one case in which the resistance produced by the tissue in a proved glimatous tumor was less than one half that of the normal brain. We have duplicated their apparatus and, from observations on twelve cases at the operating table and