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II.

IN

WATER, TEA, COFFEE, COCOA.

N importance to health second only to pure air is the quality of the water drunk. It may be even considered as a food, for there is at least a probability that its office in the system is more than that of a regulator of temperature and a diluent of the blood. From a sanitary point of view, next in importance to the quality of the water used is that of the other liquids which are more and more frequently substituted for it, namely, tea, coffee, and cocoa. Beer and wine are neither foods nor necessary beverages in this land of good water and cheap coffee, hence they are not here considered.

WATER.

This section is composed of extracts taken, by permission, from "Water Supply, Chemical and Sanitary,” by William Ripley Nichols.

Drinking Water and Disease.

With reference to their use for town and household supply, we shall roughly divide all natural waters into four classes, as follows:

1. Rain water;

2. Surface water, including streams and lakes; 3. Ground water, including shallow wells;

4. Deep-seated water, including deep wells, artesian wells, and springs.

Under each of these heads we shall study the advantages and disadvantages of the particular class of water, the liability of pollution, etc.; but first we will consider, in a general way, the connection which exists, or is supposed by some to exist, between drinking water and disease.

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A water containing a considerable amount of dissolved substances, one which could properly be denominated a mineral water, would not be thought of for a public water supply; and would seldom be used as a regular beverage except for the sake of real or fancied medicinal effect; a small amount, however, of mineral matter is generally considered an advantage. The presence of the substances which ordinarily exist

in solution in natural waters must not be regarded as necessary, because on shipboard experience has shown that distilled water, properly aerated, is perfectly wholesome. It appears that distilled water, soft surface water, and moderately hard spring or well water are all wholesome, and may be drunk without inconvenience by persons accustomed to their use. It is, however, true that a person who is in the habit of drinking a soft water generally experiences some derangement of the digestive organs on beginning to use hard water, and vice versa. It is contended by some that the human system needs salts of lime, etc., that these compounds are furnished in an assimilable form in water, and that, consequently, a somewhat hard water is more advantageous for town supply. Statistics have been brought together to support this view by comparing the death rate of various towns with the hardness of the water supply; but the death rate depends upon too many factors to be used as the chief argument in this connection. It is, however, the result of general observation, that a hard water of which the hardness is due to salts of magnesia or to sulphate of lime is not well suited for drinking, and is injurious to most persons.

A hard water is, generally speaking, one which contains compounds of lime or magnesia in solution.

Waters, especially surface waters, containing much vegetable matter are also, in some cases, unwholesome. The water of marshes is sometimes the cause of diarrhoea and other diseases of this character, and is supposed by some to cause malarial fevers. The mere presence of vegetable organic matter, however, is not sufficient to produce these effects, because many waters which are quite deeply colored by vegetable matter are proved by experience to be perfectly wholesome.

While some waters are thus in their natural condition unwholesome, and may be the cause of sickness, the attention of sanitarians and water experts is directed nowadays principally to the effect of water which is polluted by the waste materials from manufactories and dwellings, or by the sewage of towns and cities; and it is generally held, especially in England and the United States, that water thus polluted may be, and frequently is, the cause of certain specific diseases. Before discussing this question directly, it is important to have a general idea of the present prevailing view with reference to the so-called zymotic diseases, and to understand what is meant by the "germ theory."

Many clear liquids containing organic matter of animal or vegetable origin, — such, for instance, as infusions of hay, infusion of turnip, urine, etc., - if exposed to the air, gradually become turbid or cloudy; or perhaps a film forms on the surface of the liquid, or a deposit upon the walls of the vessel which contains it. The cause of the turbidity is shown by the microscope to be the presence of countless minute organized bodies, some rod-like, others globular, — which prove to be capable of self-propagation, and which are endowed with motion, at least under certain conditions. Similar organisms are found in the "dust" which floats in the air, and which may be collected by causing a current of air to impinge upon a surface moistened with glycerine; they occur in rain water, particularly in that which falls in the beginning of a shower, in surface waters, and elsewhere. They are found especially where there is decomposing organic matter, and perform an active part in promoting or producing the chemical changes which take place. In certain diseases of men and of the lower animals, organisms which, in their general character, are similar to those thus described, have been found in the blood or in the substance of various organs, and their con

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