Disposable cartridge for an assay of a biological sample

A cartridge is provided to present a biological sample for analysis by an imaging instrument. The cartridge of the invention utilizes a series of channels, capillaries, reservoirs and stop junctions to precisely move a sample, reagent and diluent through the cartridge as a function of the sum of capillary, gravitational and low centrifugal forces. The operator applies a precise amount of sample to the cartridge; therefore, the cartridge fluidics need not meter the sample prior to dilution. A practical and cost effective cartridge and assay process is disclosed which overcomes many of the limitations of the prior art. Such a cartridge is especially useful with fixed volume assays which permit low centrifugal accelerations to move the fluids within the cartridge.