Od (from the same root as Odin and supposed to mean all-pervading), the name given by baron Reichenbach to a peculiar physical force which he thought he had discovered. This force, according to him, pervades all nature, and manifests itself as a flickering flame or luminous appearance at the poles of magnets, at the poles of crystals, and wherever chemical action is going on. This would account for the luminous figures said to be sometimes seen over recent graves. The od force has positive and negative poles, like magnetism. The human body is od-positive on the left side, and od-negative on the right. Certain persons, called "sensitives," can see the odic radiation like a luminous vapor in the dark, and can feel it by the touch like a breath. As the meeting of like odic poles causes a disagreeable sensation, while the pairing of unlike poles causes a pleasant sensation, we have thus a sufficient cause for those likings and antipathies hitherto held' unaccountable. Some sensitive persons cannot sleep on 'their left side (in the northern hemisphere), because the north pole of the earth, which is od- negative, affects unpleasantly the od-negative left side. All motion generates od; why, then, may not a stream running underground affect a sensitive waterfinder, so that the divining-rod in his or her hand shall move without, it may be, any conscious effort of will? All the phenomena of mesmerism are ascribed to the workings of this od-force. Reichenbach does not pretend to have had the evidence of his own senses for any of those manifestations of his assumed od-force; the whole theory rests on the revelations made to him by "sensitives." It may be added that few if any really scientific men have any belief in the existence of such a force. Those curious in such matters are referred for the details of the subject to Reichenbach's large work, translated into English by Dr. Ashburner, under the title of The Dynamics of Magnetism, or to a briefer account in his Odisch — Magnetische Briefe (Stutt. 1852). See also Lond. Qu. Rev. Oct. 1871, p. 162. SEE ODYLISM.