Page:Collected Physical Papers.djvu/275

Rh continues for a short period even after the cessation of stimulation; it attains a maximum after which

the substance begins to recover, at first quickly, then more slowly. In all this, an analogy is found with the response curve of muscles, in which also there is a short phase of latent period, a phase of increasing action and a phase of recovery.

Three sets of experiments were carried out (1) on the effect of succession of maximum stimuli; (2) on the summation-effects of medium stimuli with slow intermittence; and (3) on the summation-effects of rapid intermittence.

Maximum stimulation.—By bringing the radiator sufficiently near the inorganic receiver, a maximum effect was observed, the deflection being 230 divisions. Before the substance could recover to any extent, a second stimulus was superposed. This produced no further deflection, but when the second stimulus was applied after recovery, then the second deflection was the same as the first, i.e., 230 divisions.