Page:Life Movements in Plants.djvu/157

Rh experiment on animal nerve is similar to that employed for the corresponding investigations on the plant. The choking coil is used to prevent the stimulating induction current from getting round the circuit of constant current. The specimen is held on an ebonite support, and every part of the apparatus insulated with the utmost care.

In the case of the conducting tissue of the plant a very striking proof of the influence of the direction of current on conductivity was afforded by the induced variation of velocity of transmission. Equally striking is the result which I have obtained with the nerve of the frog.

Experiment 44.—The experiments described below were carried out during the cold weather. The following records (Fig. 49), obtained by means of the pendulum myograph, exhibit the effect of the direction of current on

49.—Effect of heterodromous and homodromous current in inducing variation in velocity of transmission through nerve. N, normal record; upper record shows enhancement, and lower record retardation of velocity of transmission under heterodromous and homodromous currents, respectively.

the period of transmission through a given length of nerve. The latent period of muscle being constant, the variations