A drop of each of the following, is placed separately on four...

Serum is the component of blood which does not play a role in clotting. Serum includes all proteins not used in blood clotting; all electrolytes, antibodies, antigens, hormones; and any exogenous substances (e.g., drugs or microorganisms). Blood serum = Blood $-($ cell + clotting factors) Caution Serum is the liquid that remains after the blood has clotted. Plasma is the liquid that remains when clotting is prevented with the addition of an anticoagulant.