Conduction and Contraction in the Column of Hydra

Abstract

1. A suction electrode is described which allows long-term recording of spontaneous activity from essentially unrestrained Hydra. These electrodes were used to hold the animal while measuring column contractions and to measure the conduction velocity of the electrical potentials (contraction pulses = CPs) associated with contraction. 2. CPs are conducted in the column at 3.4-8.1cm./sec. The conduction velocity generally differs in the basal and hypostomal directions but the direction of faster conduction varies from animal to animal. 3. The latency between CPs and measurable column contraction is 0 1-0.15 sec. During isometric contractions following single CPs there is a rapid tension rise reaching a peak in about 1 sec. which is usually followed by partial relaxation and then a second, slower tension rise. Available evidence indicates that both tension components are due to contraction of longitudinal musculature and both are activated by the same conducting system.