The following studies will be undertaken: (A) To determine lymph flow from the mesenteric lacteal ducts of the cat intestine during fluid absorption. A large increase of lymph flow from the main intestinal lymph duct adjacent to superior mesenteric artery has been frequently reported in the literature, but this duct may also drain the lymph from the liver due to communications between intestinal and hepatic lymphatics as recently found in most rats and probably also in cats and dogs. Therefore, the lymph flow from the mesenteric lacteal ducts during fluid absorption will provide direct evidence concerning the role of the lymphatic system in fluid transport. (B) To determine protein concentration and osmolarity of the lymph formed in the intestinal villi under various conditions. The lymph is collected by micropuncture of the villus lymph capillary (central lacteal). Lymph osmolarity is determined by nanoliter osmometer (Clifton Physics) and protein concentration by ultramicro analysis with biuret reagent.