Volume 2
The household physician : a family guide to the preservation of health and to the domestic treatment of ailments and disease, with chapters on food and drugs and first aid in accidents and injuries / by J. McGregor-Robertson ; with an introduction by John G. McKendrick.
- M'Gregor-Robertson, J. (Joseph), 1858-1925
- Date:
- 1899
Licence: Public Domain Mark
Credit: The household physician : a family guide to the preservation of health and to the domestic treatment of ailments and disease, with chapters on food and drugs and first aid in accidents and injuries / by J. McGregor-Robertson ; with an introduction by John G. McKendrick. Source: Wellcome Collection.
131/656 (page 641)
![IMPUEITIES IN WATER. tures, washed into the water of a stream, for ex- ample, by the rain, or from dead animal matter also, undergoing gradiil^l decay in the fields and ditches, or in the stream itself, oi it may be derived from human excreta and the refuse of human habitations, owing to the opening of sewers into the stream, or owing to the trick- ling of the liquid from a dungheap, for example, finding its way into a well. Of all sources of pollution, the last is the most serious. Now, the nature of the impurities thus cast into water will be readily understood. To take one illus- tration, urine contains in solution (see p. 292) chiefiy urea, a nitrogenous body, the product of the oxidation of albuminous food-stuffs in the body, uric acid, also a nitrogenous body, com- mon salt, phosphates of soda, and other com- pounds of phosphoric acid, sulphates, &c. Now, if sewage is gaining access to a water supply to any extent, cdmmon salt, phosphates, and sul- phates, will be found in the water in greater quantity than is usual in ordinary water, de- rived from the urine, and the unusual quantity of these inorganic, and in themselves harmless, constituents would raise suspicions in an an- alyst’s mind as to the purity of the water. Further, he will be able to detect the presence of a substance containing nitrogen, derived from the urea and uric acid. If he can determine in what form the nitrogen is present, he will ob- tain a good idea of its source. Everyone knows that if urine stands for a time, it decomposes, becomes muddy, and gives off an offensive am- moniacal smell. This is because, under the influence of atmospheric organisms, the urea becomes converted into carbonate of ammonia. All the urea might thus become transformed, and be no longer found as such; but the fact that an organic body had been present would be signified by the detection of the ammonia, which is formed of the nitrogen fornmidy ex- isting as urea, and originally derived from albuminous food. With the lapse of more time, further changes would occur, still further alter- ing the form in which the niti’ogen existed; these changes being due, as already noted, to oxidation process, the tendency of all the change being to break down hurtful organic .bodies into harmless and simple inorganic substances. Albuminous substances themselves gain access to water, and may be detected by the chemist as such, but they undergo in course of time the same transforming process by the agency of the dissolved oxygen of the water. Thus in search- ing for impurities in water, the chemist tests for albuminoid substances themselves. If they exist beyond the barest trace, that implies that the water is contaminated with material which nature has not yet had time to reduce to simple and harmless forms. Such water is not fitted for domestic purposes, unless purified by some means, and stands, therefore,condemned. Should, however, his tests fail to find such organized material he tests for ammonia, for nitrites, for nitrates, in short, for the substances which would result from the presence of organic im- purity, if there had been time for oxidation to occur. If these are found, in any amount, the fact that at some part of its com-se the stream is contaminated is established, although before it reached the place where the water was taken for analysis nature had had time to effect her purifying processes. Now, the mere presence of albuminoid ma- terial or of its oxidized products does not necessarily render water impure. There is no manner of doubt that such polluted water is continually being used for domestic and drink- ing purposes, and without harm often result- ing. It is not even the quantity of such im- purity that determines the unwholesomeness of the water, for one well may be largely con- taminated with sewage, and may be consumed without doing any perceptible injury; another, in its neighbourhood, may be so slightly con- taminated, that the detection of any impurity in it is a matter of difficiilty, and yet it may bring disaster to every household using it. It is the exact nature of the organic pollution that makes the difierence, a difference which may be absolutely undetectible by the most delicate tests, and yet may be appalling in its results. Take an illustration: a farm possesses a weii, in the immediate neighbourhood of which the dungheap is foolishly permitted to lie. All the waste water and excreta from the farndiouse, all the manure from the stables and byre, &c., are thrown on this heap. The watery portions from the heap filter through the ground and frain access to the well. The water of the well is used by the ])eople of the farm for their own domestic purposes, for washing milk-cans, and so on. This state of things may last for years and no one be apparently any the worse of the polluted state of the well. But one of the farm hands takes typhoid fever and is nursed at the farm. The excreta from the patient are also thrown on the heap, and filter into the well. The pollution of the well is not altered in quantity, it is no more than it has been for years, but it is altered in character. A peculiar ! character has been imparted to it, marked by](https://iiif.wellcomecollection.org/image/b28124674_0002_0131.jp2/full/800%2C/0/default.jpg)
