. An introductionto physiology. normal saline solution in two beakers. In eachlet the brush of a non-polarizable electrode the electrodes through the usual short-circuiting key with the electrometer. Bring themeniscus into the field. Let an assistant placea finger of each hand in the saline solution. When the short-circuiting key is opened themeniscus will be displaced by the skin (secretion)current. Careful observation will show also aperiodic variation synchronous with the systoleof the heart. The diphasic character of the action current ofthe heart, shown so well by the capillar
. An introductionto physiology. normal saline solution in two beakers. In eachlet the brush of a non-polarizable electrode the electrodes through the usual short-circuiting key with the electrometer. Bring themeniscus into the field. Let an assistant placea finger of each hand in the saline solution. When the short-circuiting key is opened themeniscus will be displaced by the skin (secretion)current. Careful observation will show also aperiodic variation synchronous with the systoleof the heart. The diphasic character of the action current ofthe heart, shown so well by the capillary elec-trometer to the unaided eye, appears even moreclearly when the movements of the meniscus arerecorded by projecting them on a quickly movingphotographic plate. By photography, too, the di- 176 THE PHYSIOLOGY OP MUSCLE AND NERVE phasic character of the action current in the morerapidly contracting skeletal muscle is made visible,and the form of the action current wave the capillary electrometer was used for. Fig. 48. Scheme of differential rheotome. this purpose, the differential rheotome of Bern-stein was employed. This celebrated inventionconsists of a wheel which revolves at uniformspeed and carries contacts by which the primarycircuit of an inductorium and a galvanometer THE ELECTROMOTIVE PHENOMENA 177 circuit may be made. By means of the induc-torium, the muscle is stimulated at one galvanometer records the current of actionby means of electrodes placed at the other endof the muscle. The position of the galvanometercontact on the wheel can he shifted nearer to orfarther from the stimulating contacts; thus theinterval between stimulation and the making ofthe galvanometer circuit may be chosen at will,and the electromotive force at any point in theaction wave registered. By repeatedly changingthe interval, the several portions of the wavecan be investigated successively, and the resultsplotted. With Hermanns rheotachygraph, thewhole electrical ch
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