Serum separator and fibrin filter

An article for drawing and holding a blood sample and adapted to be centrifuged to thereby position a separator between the packed cell portion of the blood, the heavier phase, and the serum or plasma portion, the lighter phase. The article includes a rigid evacuated tubular container hermetically sealed with a removable resilient stopper, an inner cover element within the container detachably connected to the stopper to be separated therefrom on centrifugation of the blood sample, the element having plural filter openings therein, and a quantity of an inert semifluid sealant in the bottom of the container, the cover element and the sealant each having a specific gravity greater than the serum or plasma portion but less than the packed cell portion. In centrifuged position, the cover element intimately overlies the sealant and is supported from the wall structure of the container by the sealant, the sealant closing the filter openings and forming with the cover element the separator.