of these other troubles; or he can remove such infections speedily should they once appear. Pure sweet milk is only a question of sufficient care. But care means labour and expense. As long as we demand cheap milk, so long will we be supplied with milk procured under conditions of filth. But when we learn that cheap milk is poor milk, and when we are willing to pay a little more for it, then only may we expect the use of greater care in the handling of the milk, resulting in a purer product. Bacteriology has therefore taught us that the whole question of the milk supply in our communities is one of avoiding the too rapid growth of bacteria. These organisms are uniformly a nuisance to the milkman. To avoid their evil influence have been designed all the methods of caring for the dairy and the barn, all the methods of distributing milk in ice cars. Moreover, all the special devices connected with the great industry of milk supply have for their foundation the attempt to avoid, in the first place, the presence of too great a number of bacteria, and. in the second place, the growth of these bacteria. BACTERIA IN BUTTER MAKING. CREAM RIPENING.--Passing from milk to butter, we find a somewhat different story, inasmuch as here bacteria are direct allies to the dairyman rather than his enemies. Without being aware of it, butter makers have for years been making use of bacteria in their butter making and have been profiting by the products which the bacteria have furnished them. Cream, as it is obtained from milk, will always contain bacteria in large quantity, and these bacteria will grow as readily in the cream as they will in the milk. The butter maker seldom churns his cream when it is freshly obtained from the milk. There are, it is true, some places where sweet cream butter is made and is in demand, but in the majority of butter-consuming countries a different quality of butter is desired, and the cream is subjected to a process known as "ripening" or "souring" before it is churned. In ripening, the cream is simply allowed to stand in a vat for a period varying from twelve hours to two or three days, according to circumstances. During this period certain changes take place therein. The bacteria which were in the cream originally, get an opportunity to grow, and by the time the ripening is complete they become extremely numerous. As a result, the character of the cream changes just as the milk is changed under similar circumstances. It becomes somewhat soured; it becomes slightly curdled, and acquires a peculiarly pleasant taste and an aroma which was not present in the original fresh cream. After this ripening the cream is churned. It is during the ripening that the bacteria produce their effect, for after the churning they are of less importance. Part of them collect in the butter, part of them are washed off from the butter in the buttermilk and the subsequent processes. Most of the bacteria that are left in the butter soon die, not