Anæsthetics likewise have the effect of slowing the rate of contraction-waves before blocking them. Taking, for instance, the case of chloroform, a narrow spiral strip between one and two feet long was immersed in sea-water containing a large dose of the anæsthetic; the observations being taken at six seconds' intervals, the following were the results:—
Fig. 18.
In such experiments, the recovery of the normal rate in unpoisoned water is gradual. Taking, for instance, the case of a spiral strip in morphia (Fig. 19), it will be seen that the original rate did not fully return. Some substances, however, exert a more marked permanent effect of this kind than do weak solutions of morphia. Here, for instance, is an experiment with alcohol (see Fig. 20).
Fig. 19.
Fig. 20.