Chapter II: Washed White Blood-Corpuscles

The finger or lobe of the ear is punctured as in making a blood count, and the blood is allowed to drop directly into normal saline, ·85 per cent. solution, containing about 1 per cent. sodium citrate; this decalcifies the blood and prevents clotting. The corpuscles are completely precipitated in the centrifuge, and then repeatedly washed with ·85 per cent. saline and centrifugated, until all traces of the citrate and serum are removed. After the final precipitation the saline solution is withdrawn, and the thin upper grayish layer of the sediment, the leucocytic cream, consisting for the most part of washed white blood cells, is removed.