SummaryBy the method of Florkin and Duchateau, it is possible to separate five protein fractions in the serum.That method has been used for the study of the proteinic changes during various hepatic diseases (catarrhal jaundice, postarsphenamine jaundice, cirrhosis).Nearly constantly, it shows an increase of the second globulinic fraction, the greater the more important was the hepatic damage.A marked decrease of the albumins, exclusively of the 5thfraction, has been noticed in cirrhosis and in postarsphenamine jaundice.The statistic study, which has been made up, shows with evidence that these changes are pathologic.Several tets of hepatic insufficiency have been performed (tests of Hanger, Takata, Weltmann and Gross).A parallelism between the increase of the second fraction and the intensity of the floculation tests was noticed.