What has already been said affords ample reason for a wider dissemination of the elementary facts of bacteriological science. But there are other reasons of a more practical nature. Municipalities are expending public moneys in water analysis, in the examination of milk, in the inspection of cows and dairies, in the bacterial treatment of sewage, and in disinfection and other branches of public health administration. Again, the newly formed National Association for the Prevention of Tuberculosis, our increasing colonial possessions with their tropical diseases, even medical science itself, which is year by year becoming more preventive, make an increasing claim upon public opinion. The successful accomplishment and solution of these questions depend in a measure upon an educated public opinion respecting the elements of bacteriology. Recently it was urged that "the first elements of bacteriology should be shadowed forth in the primary school."[1] This course was advised owing to such knowledge being of value to those engaged in dairying. As we shall point out at a later stage, many of the undesirable changes occurring in milk are due to bacteria, even as the success of the butter and cheese industries depends on the use and control of the fermentative processes due to their action. Much of the uncertainty attending the manufacture of dairy products can only be abolished by the careful application of some knowledge of the flora of milk. In Denmark and in Scandinavia the importance of such knowledge is realised and acted upon. America, too, has not been slow to respond to these needs; but in England comparatively little has been done in this direction.[2] Whilst there can be no doubt as to the advantage of a wider dissemination of the ascertained facts concerning bacteria, it should be borne in mind that only patient, skilled observation and experimental research in well-equipped laboratories can advance this branch of science, or indeed train bacteriologists. The lives of Darwin and of Pasteur adequately illustrate this truth. Yet it is observable that States and public bodies are slow to act upon it, and frequently in the past the most useful and substantial support for the advancement of science has been forthcoming only from private sources. As the world learns its intimate relation to science and the interdependence between its life and scientific truth, it may be expected more heartily to support science. BACTERIA CHAPTER I _THE BIOLOGY OF BACTERIA_[3]