In previous investigations1 with standardized curare2 one of us (A. E. B.) has called attention to the similarity of the action of curare and the symptoms of myasthenia gravis. After these clinical observations we discovered the same hypothesis had been suggested by others: Oppenheim3 in 1901 observed that "veratrine evoked in muscles a condition analogous to myasthenia"; Briscoe4 in 1936 showed that mild curarization produced a myogram similar to that of myasthenia gravis, and later Harvey and his co-workers5 confirmed this similarity and stated, "The characteristic abnormalities of the electrical responses of the myasthenic and curarized muscle are identical in all respects." From the analogy between myasthenia gravis and partial curarization he suggested the hypothesis that a circulating inhibitor substance may arise from the thymus gland. Harvey and his associates6 concluded:
All of the experimental work, therefore, points to the similarity of myasthenia to