THE subject of immune sera has not in this country received as much attention from the medical profession as its importance and interest deserve. This is not so much due to the inherent difficulties of the subject as to the complicated way in which it has usually been expounded, and to the fact that the nomenclature introduced by different authors, and experimenters has been found bewildering. The difficulties have been increased by the introduction by various experimenters of different terms for the same entities, and often ones which suggest the function or properties of the substance, according to the inventor's particular views. Immune Sera. Haemolysins, Cytotoxins, and Precipitins. By Prof. A. Wassermann Translated by Charles Bolduan, M.D. Pp. ix + 77. (New York: John Wiley and Sons; London: Chapman and Hall, Ltd., 1904.)