Serum \Se"rum\ (s[=e]"r[u^]m), n. [L., akin to Gr. ???, Skr.
   s[=a]ra curd.] (Physiol.)
   (a) The watery portion of certain animal fluids, as blood,
       milk, etc.
   (b) A thin watery fluid, containing more or less albumin,
       secreted by the serous membranes of the body, such as the
       pericardium and peritoneum.
       [1913 Webster]

   Blood serum, the pale yellowish fluid which exudes from the
      clot formed in the coagulation of the blood; the liquid
      portion of the blood, after removal of the blood
      corpuscles and the fibrin.

   Muscle serum, the thin watery fluid which separates from
      the muscles after coagulation of the muscle plasma; the
      watery portion of the plasma. See Muscle plasma, under
      Plasma.

   Serum albumin (Physiol. Chem.), an albuminous body, closely
      related to egg albumin, present in nearly all serous
      fluids; esp., the albumin of blood serum.

   Serum globulin (Physiol. Chem.), paraglobulin.

   Serum of milk (Physiol. Chem.), the whey, or fluid portion
      of milk, remaining after removal of the casein and fat.
      [1913 Webster]