. A practical treatise on medical diagnosis for students and physicians . lass jar, D, in which the dilution is made ; (4) a smallglass stirrer, E, for mixing the blood and diluting fluid in the jar; (5) asmall lancet, F; (6) a brass stage-plate, C, carrying a glass slip on whichis a cell I mm. deep. The bottom of the cell is divided into ^ On the top of the cell rests the cover-glass, which is kept inplace by the pressure of two springs proceeding from the ends of the H^EMOCYTOMETERS. 569 stage-plate. 995 of the diluting fluid are measured and blown intothe rnixing-jar; then
. A practical treatise on medical diagnosis for students and physicians . lass jar, D, in which the dilution is made ; (4) a smallglass stirrer, E, for mixing the blood and diluting fluid in the jar; (5) asmall lancet, F; (6) a brass stage-plate, C, carrying a glass slip on whichis a cell I mm. deep. The bottom of the cell is divided into ^ On the top of the cell rests the cover-glass, which is kept inplace by the pressure of two springs proceeding from the ends of the H^EMOCYTOMETERS. 569 stage-plate. 995 of the diluting fluid are measured and blown intothe rnixing-jar; then 5 of blood are added and the two thoroughlymixed. A small drop of the mixture is then placed upon the cell, thecover-glass gently adjusted and held in place by the springs. From fiveto ten minutes should be allowed to elapse, so that the corpuscles will havetime to settle to the bottom of the cell. The stage-plate is then placedunder a microscope, and the number of red blood-cells in 10 squarescounted. This number multiplied by 10,000 gives the number in a cubic. Hsemocytometer of Gowers. centimetre of pure blood. It is better to count a large number of squares,take the average, and multiply by 100,000. This number is the productof the dilution (200) by the square surface of the cells, 100 (10 X 10),and again by 5, the depth of the cell: 200 X 100 X 5 = 100,000. Tofacilitate seeing the fine lines marking the squares, a soft black lead-pencilshould be gently rubbed over them before the drop of diluted blood isplaced on the cell. Counting of the white cells is made much easier if thediluting fluid is colored a pale violet with a very small quantity of gentian-violet. The white cells then appear a distinct blue, while the red cells areunaltered. As diluting fluids, a 1 per cent, solution of common salt, or per cent, solution of potassium dichromate, as recommended byDaland, may be employed; or Toissons fluid can be used. It is madeas follows : distilled water, 160
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