Lymph is a clear to pale-white, coagulable fluid that circulates throughout the lymphatic system. It is formed when the interstitial fluid, which lies in the interstices of all body tissues, is collected through lymph capillaries. Lymph consists of white blood cells, especially lymphocytes, which are the cells that attack bacteria and viruses, and it also contains proteins, glucose, and other organic and inorganic substances. The main role of the lymphatic system is to act as a filter against microbes, organic and inorganic substances, and to transport nutrients to the cells, enable intercellular communication between the cells, and remove metabolic wastes from the cells. The interstitial fluid is collected by the lymphatic system, and the rest is drained out. The drained fluid moves back to the blood vessels, and the remaining fluid is collected through the lymph capillaries, which is also known as lymphatic capillaries. Lymph is transported through larger lymphatic vessels to lymph nodes, where it is cleaned by lymphocytes, before emptying ultimately into the right or the left subclavian vein, where it mixes back with the blood.