IT has long been known that proteins differ widely in their rates of migration in an electric field, and many attempts have been made to use this phenomenon for purposes of separation and identification by so-called 'electrophoresis'. The principle is particularly attractive since even highly unstable substances are unlikely to be damaged by the treatment. One is therefore at first surprised at the scanty results yielded so far by so promising a method. The reason is that until recently no apparatus had been designed which could claim to have overcome the many technical difficulties. In the last few years, however, there has been steady improvement in this respect, associated largely with the names of Dr. Theorell of Stockholm and Prof. Tiselius of Uppsala. The latest form of Tiselius apparatus, which has now been placed on the market by Messrs. F. Hellige and Co., of Freiburg, enables the separation to be followed both optically and analytically, while the resolving power for small differences of mobility has been greatly increased. A direct result of these improvements has been the detection and isolation of the three components of serum globulin (Tiselius, Biochem. J., 31, 1464; 1937) which has answered an old and much disputed question. The apparatus is already in use in several other laboratories, and promises a host of further interesting results, for example, in the study of pathological sera, immune bodies and enzymes.