particularly those directed towards the anodic and in less degree also those towards the cathodic pole. This excitation, greatest at the time of “making” of the current, though diminishing rapidly in intensity during its continuance, remains, however, to a less degree, and leads to a progressive disintegration of the protoplasm on the side towards the anode, which lasts until the current is again broken. (Figure 6.) Thus even though there can be no doubt, on the one hand, that the effect of stimulation, which appears at the moment of the entrance, is to produce alterations, which develop very rapidly, and that by a continuation of this state there is a more or less rapid fall to a low level; on the other hand, it is just as certain that the alterations in the living system persist throughout the duration of the changed external conditions, or to put it more concisely: the effect of the stimulus never wholly disappears unless the changes in the external vital conditions return to their original state. [35] _Du Bois-Reymond_: “Untersuchungen über tierische electricität.” Bd. I. Berlin 1848, p. 258. [36] _Kühue_: “Untersuchungen über das Protoplasma und die Contractilität.” Leipzig 1864. _Max Verworn_: “Die polare Erregung der Protisten durch der galvanischen Strom.” Pflügers Arch. Bd. 35, 45, 1889. [Illustration: Fig. 6. _Actinosphaerium eichhornii._ Four stages showing the progressive influence of a constant current. Protoplasmic disintegration at the side toward the anode.] But more, an effect of the stimulus cannot indeed take place _without_ a certain duration of stimulation, which is related in _its_ turn to the rapidity of reaction of particular living system. This can be much more readily observed in more slowly reacting substances. _Fick_[37] first proved this fact on the muscle of the _Anodonta_. I have also been able to demonstrate the same fact in the slowly reacting sea rhizopods[38] by the use of the constant current. When _Orbitolites_ is stimulated with a constant current lasting approximately the tenth of a second, no response is seen in its extended pseudopods, which are directed towards the poles. The same is the case if the induction current is employed. Only when the constant current of the uniform strength lasts approximately .05 seconds, a barely perceptible response occurs, manifested by the sudden stoppage of the centrifugal flowing of granules in the anodic pseudopods, which, however, after the lapse of one to three seconds continues again unaltered. Should the duration of the constant current be still further prolonged, typical symptoms of contraction are seen being manifested by a heaping up of the protoplasm in the pseudopods in the form of spindles and balls, whilst the protoplasm flows in a centripetal direction towards the central cell body. (Figure 7.) [37] _A. Fick_: “Beiträge zur vergleichenden Physiologie der irritablen Substanzen.” Braunschweig 1863.