SINCE the introduction of urari twenty years back it has become more and more employed as an anaesthetic for physiological experiments. Its effects on the peripheral portions of the nervous system have been carefully studied, and are most distinct and peculiar, so much so that they seem to have diverted attention from its action on the central organs. Its effect, briefly, when injected subcutaneously, is to produce a paralysis of the motor nerves by attacking their ultimate branches. Dr. Foster, at whose suggestion these experiments were undertaken, and to whom I am indebted for much assistance, in the “Handbook for the Physiological Laboratory” establishes the following propositions:—1. “The effect of urari is to destroy or suspend the irritability of nerves, but not of muscles.” 2. “With moderate doses of urari the small branches appear to be poisoned and to have lost their irritability, while the trunks are still intact.” He also points out that “in order to bring these results out well, the dose of poison must not be more than sufficient to poison the motor nerves. Subsequent or stronger action of the poison affects the central nervous system as well.” Now it is perfectly clear that the poison produces no appreciable effect on the sensory nerves, and in consequence rash conclusions have been drawn that it also has no effect on the sensorium, and is, in fact, not an anaesthetic at all.