Physostigmine, fī-sō-stig′min, n. a poisonous alkaloid, the active principle of the Calabar bean.

Army documents show the monkeys were to be anaesthetized, injected with a nerve-blocking agent, physostigmine, and observed by Army medical personnel before receiving an antidote.

Of these two have been identified, one called calabarine, and the other, now a highly important drug, known as physostigmine—or occasionally as eserine.