The Collaborative International Dictionary of English v.0.48:

Physostigmine \Phy`so*stig"mine\, n. (Chem.)
   An alkaloid found in the Calabar bean (the seed of
   Physostigma venenosum), and extracted as a white,
   tasteless, substance, amorphous or crystalline; -- formerly
   called eserine, with which it was regarded as identical.
   [1913 Webster]

WordNet (r) 3.0 (2006):

physostigmine
    n 1: used in treatment of Alzheimer's disease and glaucoma