Principle Microbiology

The differential count gives us information on the number of different types of leukocytes in per 100 leukocytes.

The smear is made on the slide. First of all a drop is put on a slide. Then with the help of another slide the smear is prepared. The cells are counted one by one. No special slide like counting chamber or dilution fluids.

The cells are differentiated on the basis of nuclear lobes they contain. And the staining capacities of granules present in the cytoplasm.

The total count of WBCs or the leukocytes is required in the diagnosis of many diseases. The number of white blood cells is much higher in the blood. So it is requires to be diluted and the Turk's solution is used for the purpose.

Turk's solution contains glacial acetic acid which lysis the red blood cells which may interfere in the counting. And it also contains the Methylene blue which stains the nucleus of the white blood cells.

The counting is done in a specialized slides called Counting chambers. The number counter per volume is then multiplied with the dilution factor to get the final number of cells per ml in undiluted blood.

The counting chamber is shown in above figure.
Counting is done under high power microscope.