. A text-book of animal physiology, with introductory chapters on general biology and a full treatment of reproduction ... Physiology, Comparative. APPLICATIONS OP THE GRAPHIC METHOD. 189 not as yet referred to are required to demonstrate the electrical condition of muscle. The galvanometer suitable for physio- logical experiments is one having very many coils of extreme- ly fine wire, and so adapted to indicate the presence of currents of slight intensity. In order that it may be ascertained definitely that the cur- rents that deflect the galvanometer needle do not originate out- side of the
. A text-book of animal physiology, with introductory chapters on general biology and a full treatment of reproduction ... Physiology, Comparative. APPLICATIONS OP THE GRAPHIC METHOD. 189 not as yet referred to are required to demonstrate the electrical condition of muscle. The galvanometer suitable for physio- logical experiments is one having very many coils of extreme- ly fine wire, and so adapted to indicate the presence of currents of slight intensity. In order that it may be ascertained definitely that the cur- rents that deflect the galvanometer needle do not originate out- side of the muscle itself, non-polarizable electrodes very care- fully made must be used, for the contact of ordinary metallic electrodes with living tissues suffices of itself to generate an electric current, as may be simply illustrated to one's self by placing two coins, one silver and the other copper, in contact with the upper and under surfaces of the tongue respectively, and meeting in front; a peculiar taste results from the current excited. The construction of the non-polarizable electrodes common- ly employed, and as arranged for use, is diagrammatically rep- resented below (Fig. 186). Assuming the apparatus for the detection of electrical cur- rent in muscle to be in working order, a muscle from one of. FiQ. 186.—Non-polarizable electrodes of Du Bois-Eeymond (after Rosenthal. At c, clay tip, moistened with saline solution, is laid on muscle. Glass cylinder a is filled with strong solution of zinc sulphate, a good conductor, by which current is conveyed to amalgamated zinc plate b, and thence to galvanometer. the cold-blooded animals, prepared as rapidly and carefully as possible, avoiding all contact with foreign bodies, is cut across the ends transversely, and placed on pads of bibulous paper moistened with physiological ('GO-^S per cent) saline solution. The non-polarizable electrodes connected with the galvanome- ter are brought in contact with the muscle. What results depe
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