=Milking machines and farm separators.= The introduction of these special types of dairy machinery in the handling of milk on the farm has materially complicated the question of the care of milk. Both of these types of apparatus are much more complicated than the usual milk utensil; consequently, the danger of imperfect cleaning is thereby increased. This is still further accentuated by the fact that cleansing of utensils on the farm can never be done so well as at the factory or milk depot where steam is available. The milking machine may be easily kept in a comparatively germ-free condition, but unless this is done, it contributes its quota of germ life to the milk. The farm separator is more widely used than the milking machine and in actual practice the grossest carelessness prevails in the matter of its care. Frequently it is not taken apart and thoroughly cleansed, but is rinsed out by passing water through the machine. It is impossible by such a treatment to remove the slime that collects on the wall of the bowl; the machine remains moist and bacterial growth can go on. Such a machine represents a most important source of contamination of milk and cream and it is probable that the widespread introduction of the hand separator has contributed more to lower the quality of cream delivered at the factory than any other single factor. =Contamination from factory by-products.= The custom of returning factory by-products in the same set of cans that is used to bring fresh milk is a prominent cause of bad milk. Whey and skim milk are rich in bacterial life, and not infrequently are so handled as to become a foul, fermenting mass. If the cans used to transport this material are not scrupulously cleaned on the farm, transfer of harmful bacteria to the milk is made possible. In this way the carelessness of a single patron may be the means of seeding the whole factory supply. This custom is not only liable to produce a poor quality of milk, but it is more or less of a menace to all the patrons of a factory, inasmuch as the opportunity always obtains that disease-producing organisms may thus be introduced into the supply. Not infrequently is tuberculosis thus spread through the medium of factory by-products. [Illustration: Fig. 8.--Whey Disposal. Whey barrels at a Wisconsin Swiss cheese factory. Each patron's share is placed in a barrel which is so situated that it is impossible to empty it completely; thus it is not cleaned during the season.]