were, however, concealed in it. This peril from wellwater is so real that many a village which depends on wells is more in danger from typhoid fever than are large cities which supply themselves with water brought to town through pipes from some pure though distant source.

Judging by the facts, then, it begins to look as if water were encompassed by danger. So it is wherever sewage from man can in any wise reach it. For this reason we have all grown more careful about the sources of our water supply. Some cities draw it from mountain springs and from small lakes which cannot be contaminated by man. Others build huge reservoirs and protect them. Here water is stored by the hundred million gallons at a time. Other places yet filter such water as they are obliged to use from undesirable sources. For example, London, in England, must use water from the Thames. Yet as this river passes by it carries sewage from many towns on its way to sea. Nevertheless even the terrible water of the Thames is so purified by sand filters that London is remarkably free from typhoid fever.

It is raining at the present moment, and I think of the pure water that comes from the skies. Not a microbe is in it, for microbes never ascend to the clouds when water evaporates. Floating microbes may be in the air on a dusty day, but these are washed out by the first dash of raindrops. Everywhere in the world, therefore, rain water, direct from the sky, is safe to drink. And when

this water is caught in tanks and kept away from all human contamination it continues to be the safest water we have.

In deciding to live in this town or that always make some inquiry about the water supply of the different places before you come to any decision as to where to make your home. For life itself depends on the purity of our drinking-water.

Then, too, there is that other important drink, the milk we use so constantly. Even here there may be danger from harmful microbes.

In Springfield, Massachusetts, in 1882, typhoid fever suddenly appeared in several different homes at about the same time. On investigation it was found that all who had the fever took milk from the same milkman, and a little later it also appeared that a man had just had typhoid fever in the home of the farmer who sent the milk to town. Just how the microbes reached the milk no one could say. Perhaps the milk cans had been washed in water that contained the microbes. Perhaps the microbes were on the hands of the man who did the milking. Perhaps some one had put contaminated water into the cans to increase the milk supply. However it was done there was no doubt about the fact. In one way or another typhoid microbes had reached the milk and passed the disease on. Scarlet fever has sometimes been carried in the same way.

In the town where I live there is just now quite a rivalry over the milk business. Two men are trying to outdo each other in the perfection of the milk they deliver. On one neat-looking milk wagon the printed sign reads, "Clean Milk Dairy"; on the other there are but two words, "Pure Milk." As for ourselves who buy the milk, we know that from both wagons the best of milk is delivered to us. We are sure of this because both dairies believe in cleanliness. They know that the cleaner the milk the fewer the microbes, the fresher the milk the fewer the microbes, the colder the milk the fewer the microbes.

In both dairies, therefore, clean cows are kept in clean stables; they are milked by clean men who wash their hands before they do the milking. Clean pails, clean pans and bottles, all are kept fresh and sweet through the use of boiling water and "live steam." Those who conduct this business know that microbes multiply faster in warm, unclean milk than elsewhere, and that each speck of mud, each bit of horsehair, that enters the milk carries countless microbes with it. They also know that each of these microbes begins to multiply at once and that no amount of straining can take out microbes after they are once in a liquid. These men are therefore wise enough to be careful of the milk supply from the time it is drawn until it is delivered. In addition they keep it cool from start to finish.

It is quite otherwise, however, with certain men who carry on the same important business in a neighboring town. They do not seem to know that dirt and microbes go together, that the more dirt the more microbes, that the older the milk the more microbes, that the warmer the milk (before it is cooked) the more microbes. As a result their milk is not such as we should wish to use.

If at any time you are not sure about the history of your milk supply, and if you wish to make it perfectly safe, remember the old lesson that boiling kills microbes wherever they are. Two things may render milk harmful:

1. The presence of disease microbes which may reach it through carelessness.

2. The presence of too great a number of microbes which are harmless in themselves.

For young babies this last danger is the real one. Various cities are beginning to take this fact into account and are trying to supply the babies of the city with milk which carries as few microbes as possible and no danger whatever. By means of pure milk the city of Rochester, New York, reduced the death rate of its babies from one thousand in 1892 to less than five hundred in 1904. Thus one example is added to another and, the world over, fathers and mothers are learning that the kind of milk they buy helps decide what the death rate of their youngest children shall be.

1 Town and City tells how Rochester purified the milk and saved the babies.

CHAPTER XXIII

FROM FOOD TO BLOOD, OR PERISTALTIC ACTION AND THE VILLI

In the same laboratory of the Harvard Medical School and probably on the identical cats already described a second set of experiments was made to determine what the history of chyme is after it has gone through the pylorus into the tube which receives it.

This tube, which in man is about twenty feet long and about three inches around, is folded back and forth in compact compass just below the stomach. It is called the small intestine, and within it go on some of the most marvelous of our involuntary muscular contractions.

The entire scientific world was in doubt as to precisely what happens in the tube until, through the X-ray, through the cats, and through Dr. Cannon's continued experiments, the mystery was explained by the discovery of a series of surprising facts which could be readily understood.

Previously scientists had known that chyme, as it leaves the stomach, is as liquid as pea soup; that certain juices are promptly poured upon it from the liver, the pancreas, and the lining of the tube; and that in its most liquid