Lymph is a clean watery fluid like blood plasma of which composition appears like interstitial fluid but the quantity of plasma protein is less comparison to plasma. Some waste substances which originate because of the metabolism in the tissues as carbon dioxide, urea, etc are mixed in it. Some leucocytes are also found in it and they enter through thin and porous walls. Lymphocytes originated in the lymph glands are also found in big lymph vessels.
Origin of lymph:
Inside the blood vessels, the water, some quantity of proteins especially albumin and other substances originated by NILYAI contractions come in the interstitial space of cells of external tissues excreting from the capillaries because of hydrostatic pressure. This fluid is called interstitial fluid. This interstitial fluid keeps to the living tissues wet and nurtures them. Most of portion of interstitial fluid filled with waste substances as carbon dioxide, urea etc produced after nurturing the tissues reach inside the capillaries by crossing the cells of capillaries but some part of it reach into the lymphatic capillaries not going into blood capillaries which is called lymph and reaches into the blood circulation by the lymph system.