A diluting station and a pipetting station for a machine such as a biological sample testing machine. The diluting station has a rotating shot tube that fills with diluent without the need for priming when the shot tube is in a vertically inclined orientation, and which dispenses the diluent into a receptacle when the shot tube is rotated to a downward orientation. A thimble valve is placed in the shot tube to control the flow of diluent into the valve.
The pipetting station includes a cylindrical housing storing a plurality of straws and a concentric rotating drum that sweeps a straw into a straw withdrawal slot. A tubular tapered transfer pin is inserted into the straw frictional into engagement with the straw. The tubular transfer pin rotates the straw out of the slot into a generally downward orientation towards a receptacle containing a fluid. The pin and straw are lowered so as to place the end of the straw into the fluid. The fluid is withdrawn into the straw by means of vacuum applied to the tubular tapered transfer pin. The pin and straw are then raised out of the fluid. The fluid can then be deposited into a second receptacle that is moved below the straw and transfer pin by lowering the straw into the second receptacle and releasing the vacuum.