THE progress of dairy chemistry during the last two years will be reviewed under the following broad subdivisions of the subject: I, Composition of milk; II, Chemistry of the constituents; III, Physical chemistry; IV, Chemistry and technology of milk products; V, Processing; and VI, The analysis of milk and its products. Some aspects of the variation in the composition of milk have already been reviewed (Mackintosh (1)), and a fuller discussion will follow in a later review on "The Physiology of Dairy Cattle." The chemistry of the vitamins will also be dealt with in a later review on "The Nutritional Value of Milk.