STUDIES OF THE DISTRIBUTION of radioactive iodinated serum albumin (RISA) injected into the blood stream during profound oligemic hypotension demonstrated a marked rise in counting activity over the liver and splenchnic area after reinfusion of the shed blood.1 This finding was interpreted as demonstrating an increased loss of readioactive albumin into the extravascular space in theses regions following restoration of blood volume after a period of oligemia. This interpretation led to a need for more information concernign the interchange of labeled protein between the circulating plasma and the extravascular fluid. A study of the lymph from the thoracic duct was therefore thought desirable. The role of the lymph in the thoracic duct in restoration of fluid and protein to the circulating blood after hemorrhage has been stressed in previous studies.2-4 Other obesrvers, however, have noted a cessation of the flow of lymph during oligemia.5,6 The following studies were undertaken to observe the flow of lymph in dogs during and after a period of profound oligemia and to observe the exchange of radioactive