The lymph is a fluid, mostly with watery appearance, which derives from the interstitium and is absorbed by the “initial lymphatics”. It differs from the other body fluids for its high concentration in proteins and macromolecules. It has various functions, some of them still not yet clear. It plays a key role particularly in the transport of macromolecular materials, which could not be otherwise drained through blood circulation. It is also key in linking up lymph node structures and peripheral tissues, thus ensuring an adequate cell-mediated immune response. For more detailed information on lymph physical-chemical features, see a physiology text book.