Composition of blood:

1. Take few ml. of fresh blood in a test tube and before collecting the blood add a few drops of sodium oxalate or sodium citrate solution to prevent clotting. Close the test tube with a cotton plug. Leave the test tube aside for about an hour without shaking.
2. After one hour a clear, pale, straw coloured fluid separates out on the top of the red sediment in the test tube. This fluid is called plasma. Sediment contains different types of cells in the blood.
3. Carefully remove the fluid, plasma and add 10 ml of 0.9% sodium chloride to the tube with cells and mix the contents. Leave for sometime and pour out the fluid formed on the sediment. Repeat this process for 3 to 4 times.
4. Finally take a drop of the sediment on the glass slide and observe under microscope. Different cells of blood can be seen in this slide.