Abstract
Using the tracer theory of Rescigno, adapted for an open mammillary system, a method is given of finding (1) metabolic rate, (2) ratios of masses of protein in extravascular compartments to mass of protein in intravascular compartment, (3) capillary permeabilities, when 131I-labelled protein is injected into the blood stream of animals. Examples are given for human, rabbit and rat.