Abstract: Disclosed herein is a diagnostic vessel known as a pipette. The pipette includes a main pipette housing having a hollow interior defining a first chamber and a proximal end and an open distal end. The pipette includes a pipette tip assembly connectable to the main pipette housing having a hollow interior defining a second chamber, the pipette tip hollow interior having open proximal and distal ends and the first and second chambers in fluid communication. The pipette tip includes a plunger within the second chamber. Additionally, the pipette tip assembly includes structure for normally urging the plunger to a first position such that the plunger closes the distal end of the pipette tip. The structure for normally urging the plunger to a first position also allows the plunger to be urged to a second position, wherein the plunger opens the distal end and allows fluid communication from the distal end of the pipette tip through the second chamber and into the first chamber.