Elements of human physiology (1907) Elements of human physiology elementsofhumanp05star Year: 1907 APPENDIX G97 the current goes through the bridge and none through the nerve. We say then that the current is short-circuited. If however the bridge be raised, as in Fig. 314 b, the only way the current can go is through the nerve, and so the whole of the current takes this course. This form of key is indis- pensable when exciting nerves with currents of high intensity. If an ordinary make-and-break key only be interposed in the circuit, excitation may occur even when the key is raised, the curre
Elements of human physiology (1907) Elements of human physiology elementsofhumanp05star Year: 1907 APPENDIX G97 the current goes through the bridge and none through the nerve. We say then that the current is short-circuited. If however the bridge be raised, as in Fig. 314 b, the only way the current can go is through the nerve, and so the whole of the current takes this course. This form of key is indis- pensable when exciting nerves with currents of high intensity. If an ordinary make-and-break key only be interposed in the circuit, excitation may occur even when the key is raised, the current having high enough potential to complete itself through the table and stand on which the preparation lies. Diagram of Pohl's reverser. This is called unipolar excitation, and obviously cannot occur when the current is short-circuited. PohVs reverser is an arrangement for changmg the direc- tion of the current. It consists of a slab of ebonite or paraffin or other insulating material, in which are six small holes filled with mercury. A binding screw is in connection with the mercury in each of these holes. Two cross-wires (not in contact with one another) join two sets of pools together, as shown in Fig. 315. A cradle consisting of two wires joined by an insulating
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