Figure 5.14 Ridges that support coverslip To calculate number Coverslip per milliliter of sample: 12 cells×25 large squares×50×103 Number/mm2(3×102) Sample added here.Care must be taken not to allow overflow;space Number/mm3(1.5×104) between coverslip and slide is 0.02 mm Microscopic observation;all mm.Whole grid has 25 large cells are counted in large squares,a total area of 1 mm2 and square(16 small squares): Number/cm3(ml)(1.5 x 107) a total volume of 0.02 mm3. 12 cells.(In practice,several large squares are counted and the numbers averaged.) Direct microscopic counting procedure using the Petroff-Hausser counting chamberFigure 5.14 Coverslip Ridges that support coverslip To calculate number per milliliter of sample: 12 cells  25 large squares  50  103 Number/mm2 (3  102 ) Number/mm3 (1.5  104 ) Number/cm3 (ml) (1.5  107 ) Sample added here. Care must be taken not to allow overflow; space between coverslip and slide is 0.02 mm ( mm. Whole grid has 25 large squares, a total area of 1 mm2 and a total volume of 0.02 mm3 . Microscopic observation; all cells are counted in large square (16 small squares): 12 cells. (In practice, several large squares are counted and the numbers averaged.) 1 50 Direct microscopic counting procedure using the Petroff-Hausser counting chamber