The application of various bacteriologic and serologic methods to the specific diagnosis of disease is beautifully presented by Sachs. His chapter runs the gamut of the important procedures that are available. And because there is a judicious balance between method and theory of method, one is tempted to declare his review almost unique in the literature on the infectious diseases. His bibliography is sufficiently extensive to orient any one in the theoretical developments of recent years. No one using the methods of agglutination, complement fixation and bacteriolysis would remain merely a technician if he read this important contribution. The paper by Jacobsthal and Schuback includes in a brief form a convenient summary on the formed elements in the blood of the guinea-pig, rabbit, sheep, goat, dog, cow, horse, cat, pig, mouse, rat, chicken, pigeon and frog. In addition, it contains summaries on the serologic (lytic and agglutinative) properties of the