Abstract: An apparatus for transporting racks of sealed sample tubes, mixing a sample material contained within the tubes, and aspirating samples from the tubes. The apparatus includes a car which runs along a rail. The car drives racks containing the sample tubes into a mixer channel disposed above and running parallel to the rail. The mixer channel is mounted to rotate about an axis parallel to the rail to mix samples and position the tubes to be aspirated. A push pin mounted adjacent to the mixer channel extends into the mixer channel and urges individual tubes against an aspirator assembly mounted on the opposite side of the mixer channel. An input queue is disposed proximate the input side of the rail and an output queue disposed proximate the output side of rail. The input queue supports the racks and feeds them into position to be driven by the car mechanism into the mixer channel.