of stimulus. This is seen in the next two records which were taken after two hours. The amplitude of response was not only diminished, but the recovery also was incomplete.
Antagonistic actions of Alkali and Acid: Experiment 29.—Alkali and acid are known to exert antagonistic actions on the spontaneous beat of the heart; dilute solution of NaOH arrests the beat of the heart in systolic contraction, while dilute lactic acid arrests the beat in diastolic expansion. I have found identical antagonistic reactions in the pulsating tissue of Desmodium gyrans, the
Fig. 37.—Antagonistic action of alkali and acid. Arrest of response in cotraction under NaOH (↑), restoration and final arrest in expansion under actic acid (↑).
telegraph plant. It is very interesting to find that these agents also exert their characteristic effects on the response of Mimosa in a manner which is precisely the same. This is seen illustrated in Fig. 37, where the application of NaOH arrested the response in a contracted state; after this, the antagonistic effect of dilute lactic acid is seen first, in its power of restoring the excitability; its conti-
