~Use of milk-cans for transporting factory by-products.~ The general custom of using the milk-cans to carry back to the farm the factory by-products (skim-milk or whey) has much in it that is to be deprecated. These by-products are generally rich in bacterial life, more especially where the closest scrutiny is not given to the daily cleaning of the vats and tanks. Too frequently the cans are not cleaned immediately upon arrival at the farm, so that the conditions are favorable for rapid fermentation. Many of the taints that bother factories are directly traceable to such a cause. A few dirty patrons will thus seriously infect the whole supply. The responsibility for this defect should, however, not be laid entirely upon the shoulders of the producer. The factory operator should see that the refuse material does not accumulate in the waste vats from day to day and is not transformed into a more or less putrid mass. A dirty whey tank is not an especially good object lesson to the patron to keep his cans clean. It is possible that abnormal fermentations or even contagious diseases may thus be disseminated. Suppose there appears in a dairy an infectious milk trouble, such as bitter milk. This milk is taken to the factory and passes unnoticed into the general milk-supply. The skim-milk from the separator is of course infected with the germ, and if conditions favor its growth, the whole lot soon becomes tainted. If this waste product is returned to the different patrons in the same cans that are used for the fresh milk, the probabilities are strongly in favor of some of the cans being contaminated and thus infecting the milk supply of the patrons. If the organism is endowed with spores so that it can withstand unfavorable conditions, this taint may be spread from patron to patron simply through the infection of the vessels that are used in the transportation of the by-products. Connell has reported just such a case in a Canadian cheese factory where an outbreak of slimy milk was traced to infected whey vats. Typhoid fever among people, foot and mouth disease and tuberculosis among stock are not infrequently spread in this way. In Denmark, portions of Germany and some states in America, compulsory heating of factory by-products is practiced to eliminate this danger.[3]