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The technique of isolated liver perfusion has several unique features as an investigative tool for the study of hepatic physiology and biochemistry. These include the exclusion of non-hepatic tissues, the maintenance of intact cellular membranes, and the ability to control and reproduce more precisely the experimental hepatic environment than is possible in an entire animal. This investigative team has developed an isolated bovine liver peffusion preparation that is reproducible, bacterially sterile, and capable of continuous functional performance for extended periods of time.The use of a large mammal, such as the bovine calf, as the experimental animal has other useful characteristics; the large liver permits serial tissue sampling, yielding specimens of generous size. The large volume of perfusate, with little intrahepatic accumulation, allows frequent generous sampling of this medium. The use of autogenous blood as the perfusate avoids interaction between foreign proteins which could occur if blood were pooled from several homologous donors.The technique of perfusion reported herein permits simultaneous and independent perfusion through the hepatic artery and portal vein, and repetitive sampling of liver tissue and the circulating perfusate without interruption of the perfusion.This report describes the characterstics of this preparation as experienced in over 90 separate perfusion experiments.

Methods for electrophoretic separation of amino acids, peptides and proteins on filter paper were developed independently by several investigators (1-5) during the years 1948-50. The major protein components of serum could be separated satisfactorily by this principle. The serum proteins on the paper were stained with dye; by cutting the paper into segments and eluting the dye, the amount bound in each segment could be estimated and an electrophoretic pattern constructed. The quicker procedure of photometric quantitation of the resolved serum components directly from the paper strip was introduced by Grassmann, Hannig, and Knedel (6, 7). Variables which affect electrophoretic movement of protein and peptide in a paper supported buffer medium include variations in potential gradient, temperature, pH, ionic strength and nature of the buffer used, thickness of the filter paper, evaporation, time of run, and nature of the protein itself. Paper electrophoresis is well established as a research technique, having been successfully used in serum protein and lipid analysis (2-20), identification of the iron-binding globulin (21), study of gastric mucins (22), serum transport of thyroglobulin (23) and identification of abnormal hemoglobins (24, 25). This report relates experiences with the GrassmannHannig and Durrum methods of paper electrophoresis of serum proteins and photometric measurement of the amount of dye bound by the serum protein fractions. The significance of results ob-

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