Aspirating and mixing of liquids within a probe tip

Apparatus and a method for mixing a liquid within a disposable aspirating probe tip so that most of the liquid is forced to move past a transition zone between two different inside diameters to cause rotational mixing. The apparatus and method can be used to provide agglutination of blood, which in turn can be used for blood typing. The probe tip can include a single integral piece, or two separate portions. The transition zone can include a sharp demarcation between inside diameters, or a smooth one.