资料来源 : Webster's Revised Unabridged Dictionary (1913)

   2. That which is sent out, issued, or put in circulation at
      one time; issue; as, the emission was mostly blood.

   {Emission theory} (Physics), the theory of Newton, regarding
      light as consisting of emitted particles or corpuscles.
      See {Corpuscular theory}, under {Corpuscular}.