As has already been stated in the general discussion, there are many forms of diseases which are believed to be largely propagated through water. Among these the two which have been mentioned as most important are typhoid fever and cholera. The character of the organism which produces cholera is not so well understood as that which produces typhoid. The skilled bacteriologist will have no difficulty in recognizing the presence of typhoid germs and by isolating and cultivating them can reproduce them at will. Of course any water containing the typhoid germ is totally unfit for consumption. While, as has been intimated, such water may be used with impunity by some persons in vigorous health, it may at any moment seize upon one who consumes it, producing dangerous and even fatal results. The typhoid bacteria, when they do exist in water, are usually in very small numbers. It is therefore difficult to discover them. It is considered sufficient to discover other organisms which constantly accompany the typhoid germ, such as the colon bacillus and when these are found to assume that the typhoid germ may also be present and treat the water accordingly. There are many methods by which the typhoid germs enter the water. They may enter before consumption even when they are not present in the original source. When typhoid is epidemic all parts of the house and the vessels which may be in the house or near it may become infected. The water which may be brought into the house entirely free of typhoid germs, by being placed in vessels which are contaminated or polluted or otherwise exposed to infection, may become the vehicle to carry the germ in a dangerous way. The cholera bacillus is even more dangerous than that of typhoid. Fortunately it is rarely present in waters and therefore need not be feared except in cases of an epidemic. In all such cases no water should be regarded as above suspicion.