American journal of physiology . cm. The metallic tankfitted into a correspond-ing notch around theebonite base. The basehad two slits in it whichextended almost the fulllength of the slits acted asguides for the stimu-lating electrodes, thetunnel-tube, and theleading-ofif tunnel-tube was aseries. In order to make sure that the heating of the stretch b was confinedto b two additional tunnel-tubes were used, one on each side of theheating tube. Through these water was circulated of the sametemperature as that of the water supplying the tank. At first thethree tubes
American journal of physiology . cm. The metallic tankfitted into a correspond-ing notch around theebonite base. The basehad two slits in it whichextended almost the fulllength of the slits acted asguides for the stimu-lating electrodes, thetunnel-tube, and theleading-ofif tunnel-tube was aseries. In order to make sure that the heating of the stretch b was confinedto b two additional tunnel-tubes were used, one on each side of theheating tube. Through these water was circulated of the sametemperature as that of the water supplying the tank. At first thethree tubes were separate, but subsequently they were arrangedtogether so that they formed a tunnel about 34 mm. long. Aroundthe middle third of the tunnel passed warm water, around the twoend thirds tap water (Fig. 3). In this manner the nerve lay in achamber having a fairly constant temperature; the temperature ofthe stretch b could be varied, but this change of temperaturecould not be conducted along the nerve, nor could the leading-ofif. Tank Supply Beater modified form of that used in the first 312 J. C. Herrick. electrodes be unequally heated because of the interposed temperaturetube. The stimulating electrodes were platinum points, which had anebonite holder fitting into the two slits of the base of the moistchamber. In this second series, instead of the Ostwald electrodes, DuBois-Reymonds amalgamated zinc-ZnSO 4 electrodes with plugs of kaolinwere used. Great pains were taken in their manufacture, and onlythose were employed which were fairly isoelectric. They wereheld by means of a special holder which fitted into the two slits ofthe base of the chamber. The two slits thus served as a track alongwhich the stimulating electrodes, the triple tunnel-tube, and the non-polarizable electrodes could be displaced. Nine small set-screwsmade it possible to fix the electrodes and tubes firmly at any desireddistance apart — an arrangement that proved very convenient. The nerve chamber was s
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