These studies on the disadvantages of succinyldicholine are not intended to detract from what is a most useful clinical relaxant. Nevertheless, they indicate the urgent necessity to find a short-acting non-depolarizing drug., At the meeting in Venice on muscle relaxants in 1958, just such a compound (namely “Compound 41”) was described, which appealed from animal experiments to be highly promising.4 Alas! the investigations in main showed that it produced] profound histamine release with severe hypotension and tachycardia, and was quite unsuitable for clinical use. Haining5,6 has stimulated our interest in a series of tropine derivatives. By a careful pharmacological analysis he has produced several most interesting compounds. Some have had a shorter action than succinyldicholine, while others have proved much longer-acting. All have been found to act like d-tubocurarine.