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Summary The modifications put on the alcohol fractionation procedure of Nitschmann., Kistler and Lergier [8] since 1954 are communicated. The yields and purities realised were calculated from the results of about 150 fractionation runs, 100 1 of plasma each. The actual method allows the isolation of 48% of the total plasmaproteins as albumin (98% pure in electrophoretic analysis), 9,8% as γ‐Globulin (practically 100% pure) and 3,4% as clottable fibrinogen. A scheme summarizes the details of the entire procedure. Résumé Les modifications apportées depuis 1954 à la méthode de fractionnement de Nitschmann, Kistler et Lergier [8] sont décrites. Le rendement et la pureté des differents fractions ont été calculées à partir des résultats de 150 fractionnements de 100 litres chacun. La méthode actuelle permet d'obtenir 48% des protéines plasmatiques totales sous forme d'albumine (degré de pureté électrophorétique de 98%), 9,8% sous forme de γ‐globuline (degré de pureté pratiquement de 100%) et 3,4% sous forme de fibrinogène coagulable. Un schéma détaillé risume l'ensemble du procédé de fractionnement. Zusammenfassung: Die seit 1954 vorgenommenen Veränderungen der Alkoholfraktionierungsmethode nach Nitschmann, Kistler und Lergier [8] werden dargelegt. Die mit der Methode praktisch erzielten Ausbeuten und Reinheiten wurden aus den Ergebnissen von and 150 100‐Liter‐Plasma‐Ansätzen ermittelt: Nnch dem heutigen Verfahren lassen sich etwa 48% der totalen Plasmaproteine als Albumin (ungefähr 98% elektrophoretisch rein), 9,80/, als γ‐Globulin (praktisch 100prozentig rein) und 3,4% als gerinnbares Fibrinogen gewinnen. Das ganze Fraktionierverfahren ist in Form eines detaillierten Schemas zusammenfassend dargestellt.

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SUMMARY. Approximately 30 % of the nitrogen of /c-casein was soluble at pH 4-7 after the protein had been treated with rennin at pH 7 while approximately 10 % was soluble in 12% trichloroacetic acid (TCA). The material soluble in 12% TCA appeared at a slower rate initially than did the nitrogen soluble at pH 4-7 but as the reaction proceeded it was released more rapidly.Treating K-casein with urea, or repeated precipitation of the protein at pH 4-7, caused the formation of material insoluble at pH 7, apparently para-/c-casein. Both treatments appeared to free the same soluble fraction as does rennin acting in low concentration or for a short time.Low concentrations of rennin (0-07 /*g/ml) released only part of the available soluble nitrogen from 2 % solutions of whole casein at pH 7. Heating the reaction mixture appeared to restore the casein complex, the restoration being less complete the longer the reaction had proceeded.It is suggested that (c-casein is not a single protein but a complex, and that the action of rennin is first to open the secondary bonds responsible for the stability of this complex.