The Collaborative International Dictionary of English v.0.48:

Eucrasy \Eu"cra*sy\ [Gr. ?; ?, well-tempered; e'y^ well + ? to
   mix, temper: cf. F. eucrasie.] (Med.)
   Such a due mixture of qualities in bodies as constitutes
   health or soundness. --Quincy.
   [1913 Webster]