That it is conveyed through water is as certain as that the sun rises and sets. The only embarrassment in proving it lies in selecting from the swarm of instances. There is the classic case of the Swiss villages on opposite sides of the same mountain chain, the second of which drew its water-supply from a spring that came through the mountain from a brooklet running by the first village. Typhoid fever broke out in the first village, and twenty days later it appeared in the second village, twenty miles away on the other side of the mountain. Colored particles thrown into the brook on one side promptly appeared in the spring upon the other. Then there was the gruesome modern instance of Plymouth, Pennsylvania, in 1885. A single case of imported typhoid occurring on the watershed of a reservoir was followed, thirty days later, by an epidemic of eleven hundred cases in a population of eight thousand. An equally vivid instance came under my own observation. A school and a penitentiary drew their water-supply from the same power-flume, carrying a superb volume of purest water from a mountain stream. Early in the autumn a single case of typhoid appeared in a small town near the head of the flume. The discharges were thrown into the swiftly running water. Two weeks later an epidemic of typhoid broke out in the school, and three weeks later in the penitentiary. An unexpected freak, however, was the appearance of fifteen or twenty cases in another state institution farther down on the same stream, which did not draw its water-supply from the flume, but from deep wells of tested purity. This was a puzzle, until it was found that, owing to a fall in the wells, the water from the flume had been used for sprinkling and washing purposes in the institution, being allowed to run through the water-pipes only at night, while the well-water was used in the daytime. This was enough to contaminate the pipes, and a small epidemic began, which promptly stopped as soon as the cause was suspected and the flume-water no longer used. This last instance is peculiarly interesting, as illustrating how typhoid infection gets into milk, the second--though at a long interval--most frequent means of its spread. It does not come from the cow, for, fortunately, none of the domestic animals, with the possible exception of the cat, is subject to typhoid. Nor is it possible that cattle, drinking foul and even infected water, can transmit the bacillus in their milk. That superstition was exploded long ago. Every epidemic of typhoid spread by milk--and there are scores of them now on record--can be traced to the handling of the milk by persons suffering from mild forms of typhoid, or engaged in waiting upon members of the family who are ill of the disease, or the dilution of milk with infected water, or even, almost incredible as it may seem, to such slight contamination as washing the cans with infected water.