Since buffers are considered as substances which, by their presence in solution, increase the amount of alkali or acid that must be added to catme unit change in pH, the question of their occurrence in milk would be important. Clark (1) gives the following with regard to buffers: "By buffer action, we mean the ability of a solution to resist change in pH through the addition or loss of alkali or acid." Among the agents, which act well as buffers, are mixtures of weak acids or bases and their salts. Milk might be expected to have a definite buffer value, due probably to the combined effects of salts and protein matter present. Van Slyke (2) has shown that human blood has a rather definite buffer value of 0.0228 at pH of 7.4. Milk is known to bear a close relationship to blood. Both have a small amount of sugars and protein in true or colloidal solution. These together with the inorganic salts are definite enough in quantity so that both milk and blood exhibit a definite osmotic pressure as measured by the freezing point. Since blood is well buffered against rapid change in pH it might be considered that milk would also show a definite buffering effect. The importance of the buffer value of milk may be illustrated in a number of ways. In bacteriological experiments using milk as a media, if milk should have a constant or uniform buffer value, the rate of growth of bacteria could be observed by noting the acidity produced. However, if milk does not possess a very uniform buffer value at any pH range (5), the extent of growth could not be accurately made without, in each case, determining the buffer value of milk used. In a similar way the quantitative