“…and that the protein fractions were in the same relative proportions but Greenberg et al (1943), making use of radioactive isotopes, noted a hindrance to the free passage of ions and a deviation from the Donnan Law of distribution which indicated a secretory activity on the part of the choroid plexus. Kabat et al (1950) drew attention to the fact that the heavier molecules of globulin were not present in the fluid in the same ratio as in blood, since when many have noted differences in the proportions of various protein fractions (Fisk et al 1951, Hoch & Chanutin 1952, Gries et al 1953, Field 1954, Gavrilescu et al 1955, Uzman & Bering 1956, Mumenthaler & Marki 1957: in fact, one component found electrophoretically in cerebrospinal fluid, the r-fraction of Bucher et al (1952) -often called 2 -appears not to have its counterpart in serum. The pre-albumin fraction (Kabat et al 1942, Scheid & Scheid 1944, Fisk et al 1951, Hoch & Chanutin 1952, Bucher et al 1952, Gavrilescu et al 1955, Booij 1956) so readily identified in C.S.F.…”