\Zym"o*gen\, n. [Zyme + -gen.] (Physiol. Chem.)
A mother substance, or antecedent, of an enzyme or chemical
ferment; -- applied to such substances as, not being
themselves actual ferments, may by internal changes give rise
to a ferment.
      The pancreas contains but little ready-made ferment,
      though there is present in it a body, zymogen, which
      gives birth to the ferment.              --Foster.