Dispensing assembly with interchangeable cartridge pumps

A method of performing reactions on a plurality of specimens mounted on microscope slides comprising:

• providing a plurality of reagent dispensing assemblies on a rotating reagent carousel positioned over a rotating slide carousel, each reagent dispensing assembly comprising:
• a reagent reservoir;
• and
• a reagent metering chamber comprising a compressible housing suspended from the reagent reservoir to receive liquid through an inlet from the reservoir and unidirectional check valves at an inlet and an outlet, respectively, of the compressible housing;
• positioning a plurality of microscope slides on the slide carousel;
• rotating the reagent carousel and slide carousel relative to each other and relative to a hammer at a stationary dispensing station to position a reagent dispensing assembly over a selected microscope slide at the stationary dispensing station;
• compressing the reagent metering chamber with the hammer at the dispensing station to eject reagent through the outlet check valve onto the selected slide;
• and
• allowing the reagent metering chamber to revert to its native position due to resiliency of the chamber to draw reagent into the reagent metering chamber from the reagent reservoir.