Bacteriologists have been able to make out satisfactorily the connection of all these infections with different species of the bacteria. A large number of species have been found to curdle milk without rendering it acid, several render it bitter, and a number produce a "tainted" and one a "soapy" taste. A score or more have been found which have the power of rendering the milk slimy. Two different species at least have the power of turning the milk to sky-blue colour; two or three produce red pigments (Fig. 20), and one or two have been found which produce a yellow colour. In short, it has been determined beyond question that all these infections, which are more or less troublesome to dairymen, are due to the growth of unusual bacteria in the milk. These various infections are all troublesome, and indeed it may be said that, so far as concerns the milk producer and the milk consumer, bacteria are from beginning to end a source of trouble. It is the desire of the milk producer to avoid them as far as possible--a desire which is shared also by everyone who has anything to do with milk as milk. Having recognised that the various troubles, which occasionally occur even in the better class of dairies, are due to bacteria, the dairyman is, at least in a measure, prepared to avoid them. The avoiding of these troubles is moderately easy as soon as dairymen recognise the source from which the infectious organisms come, and also the fact that low temperatures will in all cases remedy the evil to a large extent. With this knowledge in hand the avoidance of all these troubles is only a question of care in handling the dairy. It must be recognised that most of these troublesome bacteria come from some unusual sources of infection. By unusual sources are meant those which the exercise of care will avoid. It is true that the souring bacteria appear to be so universally distributed that they can not be avoided by any ordinary means. But all other troublesome bacteria appear to be within control. The milkman must remember that the sources of the troubles which are liable to arise in his milk are in some form of filth: either filth on the cow, or dust in the hay which is scattered through the barn, or dirt on cows' udders, or some other unusual and avoidable source. These sources, from what we have already noticed, will always furnish the milk with bacteria; but under common conditions, and when the cow is kept in conditions of ordinary cleanliness, and frequently even when not cleanly, will only furnish bacteria that produce the universal souring. Recognising this, the dairyman at once learns that his remedies for the troublesome infections are cleanliness and low temperatures. If he is careful to keep his milk vessels scrupulously clean; if he will keep his cow as cleanly as he does his horse; and if he will use care in and around the barn and dairy, and then apply low temperatures to the milk, he need never be disturbed by slimy or tainted milk, or any