Source : Webster's Revised Unabridged Dictionary (1913)

Eserine \Es"er*ine\ (?; 104), n. [From native name of the
   Calabar bean: cf. F. ['e]s['e]rine.] (Chem.)
   An alkaloid found in the Calabar bean, and the seed of
   {Physostigma venenosum}; physostigmine. It is used in
   ophthalmic surgery for its effect in contracting the pupil.