The larger cities have also recognized the impossibility of requiring the tuberculin test of all cattle furnishing milk. Pasteurization remains the only safeguard, and it is probable that within a short time all the larger cities will require the pasteurization of all milk, except that produced under strict supervision. As previously mentioned heating causes certain changes in milk. In the treatment of market milk it is desirable to use as low temperatures as will suffice to destroy the disease-producing bacteria. It is fortunate that temperatures that will insure this result have little effect on the milk. The temperatures now recommended for pasteurization are as follows: 158 degrees F. for 3 minutes. 155 degrees F. for 5 minutes. 152 degrees F. for 10 minutes. 148 degrees F. for 15 minutes. 145 degrees F. for 18 minutes. 140 degrees F. for 20 minutes. In actual practice the milk is heated to 145 degrees for 25 to 30 minutes. The acid-forming bacteria are not completely destroyed and the pasteurized milk as a rule will undergo the same type of fermentation as raw milk. It is, however, deemed essential that all pasteurized milk be sold as such; that it be delivered to the consumer within twenty-four hours after pasteurization and that no milk be pasteurized a second time. The continuous pasteurizing machines have the disadvantage that a small portion of the milk passes through so quickly that all pathogenic bacteria therein might not be destroyed, (p. 131). This has led to the use of the "holding" process in which the milk is heated to the desired temperature and then placed in tanks where it remains at this temperature for any desired time. Every portion is thus treated in a uniform manner. If the milk is bottled after pasteurization, there remains opportunity for reinfection, possibly with typhoid bacilli. Pasteurization in the final container, the bottle, is being recommended. This is possible only when a special bottle is used with a metal cap lined with paper. =Milk distribution.= Until within recent years in the cities and at present in smaller towns, milk is largely retailed from cans which are carried on the wagons or are kept in stores. This exposes the milk to contamination from street dust and from the container furnished by the consumer. It is well recognized that every utensil with which milk is brought in contact adds more or less bacteria to it, and the less milk is handled, the better will be its condition when it reaches the consumer. Milk is now largely retailed in glass bottles which are closed with pulp caps. In some cities the bottling is mainly done in the country at the bottling station to which the milk is brought by the farmers; or it may be shipped by the producer to a distributing company, and all subsequent treatment, as pasteurization and bottling done in the city.