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muscle on these pads, the sulphate of zinc solution would irritate the muscle, and that, we shall see, produces new phenomena. We wish to examine the electrical properties of the muscle at rest. To protect the muscle. Fig. 69.—Arrangement of du Bois Reymond's troughs, a a, troughs of zinc; b, vulcanite plates for insulation; c c, paper pads; d e, clay pads; f f, connections for wires leading to galvanometer, g. therefore, we place on the pads of blotting-paper little bits of moist clay: sculptor's clay, moistened with saliva, is usually employed. Here are the troughs just as they are used by their inventor. There are many other forms of these electrodes, or instruments for leading off the electricity, adapted for special use; but