Determination of cells in blood

A method for determining the volume of red cells in a blood sample comprising:

• flowing along a conduit a predetermined volume of said sample;
• introducing a known volume of an agglutinating agent and a predetermined volume of a dye into said conduit, said agglutinating agent being characterized by a relatively high positive charge, said dye being of a material not present in blood samples of the type being determined, said dye also being of known concentration and water soluble and characterized by (1) not penetrating said cells, (2) not forming a precipitate with said agglutinating agent or with soluble components of said sample, and (3) not lysing said cells or altering the volume of said cells;
• mixing at least said sample and agglutinating agent while flowing along said conduit to agglutinate the red cells;
• decanting the agglutinated red cells from said conduit;
• and
• colorimetrically measuring the concentration of said dye in the plasma flowing along said conduit.