[175] _Tiedemann_: “Untersuchungen über das absolute Refractärstadium und die Hemmungsvorgänge im Rückenmark des Strychninfrosches.” Zeitschr. f. allgem. Physiologie Bd. X, 1910. [176] _Fr. W. Fröhlich_: “Die Analyse der an der Krebsschere auftretenden Hemmungen.” Zeitschr. f. allgem. Physiologie Bd. VII, 1907. The same: “Der Mechanismus der nervösen Hemmungsvorgänge.” Medizin. naturwiss. Arch. Bd. I, 1907. The same: “Beiträge zur Analyse der Reflexfunction des Rückenmarks mit besonderer Berücksichtigung von Tonus, Bahnung und Hemmung.” Zeitschr. f. allgem. Physiologie Bd. IX, 1909. The same: “Experimentelle Studien am Nervensystem der Mollusken 12. Summation und scheinbane Bahnung, Tonus, Hemmung und Rhythmus am Nervensystem von Aplysia limacina.” Zeitschr. f. allgem. Physiol. Bd. XI, 1910. [Illustration: Fig. 45. Lower line indicates stimuli.] [Illustration: Fig. 46. Reflex inhibition in the strychninized frog. Lower line indicates seconds, upper line stimuli. When stimulation with single shocks at longer intervals is applied, each single stimulus is effective. When faradic stimulation is used, only the first stimulus is operative, and during the further continuance of stimulation inhibition takes place in the spinal cord. ] Before going back to the cases of inhibition and explaining them by this general principle, it is necessary that we penetrate more deeply into the details of the characteristic course of the refractory period. By this means we will find the conditions which universally determine the interference in the effects of stimulation. First of all, it is self-evident that the occurrence of interference of stimulation in a living system can only take place when the succeeding stimulus is applied before the effects of the previous one have completely disappeared. Within the interval, however, which is involved from the moment of the beginning of a stimulus until its effect disappears through the self-regulation of metabolism, there is the possibility of various interference results from stimulation.