The manufacture of Swiss cheese presents a striking example of the disregard which factory operators show toward the employment of bacteriological principles. In these factories, the custom is widely practiced of apportioning the patrons' allotment of whey into individual barrels which are supposed to be emptied each day. As these barrels are, however, rarely ever cleaned from the beginning to the end of the season, they become very foul, and the whey placed in them from day to day highly polluted. It is this material which is taken back to the farms in the same set of cans that is used for the fresh milk. When one recalls that the very best type of milk is essential for the making of a prime quality of Swiss cheese, and that to secure such, the maker insists that the patron bring the product to the factory twice daily, the before mentioned practice appears somewhat inconsistent. =Treatment of factory by-products.= To overcome the danger of infecting milk from factory by-products with either undesirable fermentative organisms, or disease-producing bacteria, the most feasible process is to destroy these organisms by the application of heat. In Denmark, some portions of Germany, and in some of the states in this country, laws exist which require the heating of all skim milk before it is returned to the farm. This is done by the direct use of exhaust steam, or running the product through heaters. The treatment of whey in cheese factory practice is especially important since the warm whey must be stored for a number of hours before it is returned to the farms. Even under the best of conditions the whey is certain to be in an advanced state of fermentation when placed in the milk cans, and it only needs the infection of the whey tank with harmful bacteria to cause great loss on account of the injury of the product by these bacteria. Among Canadian factories the custom of heating the whey as it passes from the cheese vat to whey tank has been introduced, and where ever adopted has been retained, because, it has resulted in such an improvement of the cheese that the gain was much greater than the cost, which is estimated at not over fifty cents per ton of cheese. The whey is heated not to exceed 155° F.; the hot whey serves to scald the whey tank and as the mass of whey is usually quite large, it does not cool to a point where bacterial growth can take place for a number of hours. The whey is thus quite sweet when returned to the farm and has greater feeding value. The heating also prevents the creaming of the whey in the tank and thus avoids the soiling of the cans with grease which is most difficult to remove.