A direct study of the isolated rat liver perfused with oxygenated blood containing amino acids and lysine-ϵ-C14 has yielded facts indicating that the liver synthesizes practically all the plasma fibrinogen, the albumin fraction, and probably more than 80 per cent of the plasma globulin fraction. The response of the isolated perfused liver in protein synthesis is qualitatively and quantitatively analogous to that of the intact animal, notably in (a) the ability to discriminate between natural L-lysine and D-lysine, (b) the per cent of isotopic amino acid converted to CO2, (c) the per cent utilized in liver and plasma protein synthesis. The results obtained with the perfused liver are compared and contrasted with those reported for tissue homogenates, minces, and slices.

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A recent report (1) presented direct evidence for the dominant role of the liver in the production of plasma proteins, as studied in the isolated peffused organ, and compared the results with those obtained in intact living animals.This paper describes an attempt to assess the comparative role of the extrahepatic tissues in plasma protein synthesis. For this purpose, ten "carcass ''t perfusions have been carried out, using in general the same apparatus, lysinee-Ct% and methods previously described (1). Here again comparisons are made with results obtained in intact animals. The data show that the extrahepatic tissues produce but very small amounts of plasma protein, entirely of the nature of globulins, despite the incorporation of large amounts of lysine-e-C ~ into tissue protein.In order to define more dearly the plasma proteins produced by the nonhepatic tissues, plasma from eviscerated surviving rats injected with lysine-~-C u has been fractionated by the technique of preparative zone electrophoresis (2). The non-hepatic tissues of the eviscerated rat incorporate the labeled lysine chiefly into the plasma proteins with the mobility of the gamma globulins. The

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