CHAPTER XXXII PUBLIC SUPPLIES OF FOOD, WATER, AND GAS. (Part 2)

pollution is due to a mere dilution of the filth with purer water, and such dilution may greatly improve or even “ purify” it. A drop of ink in a quart of water makes a mixture far less inky than the original drop. On the other hand, dilution does not necessarily mean destruction. A flock of birds may be lost sight of, but not destroyed, by scattering, and. the purification of sewage filth should mean its destruction as such and its conversion into harmless substances. Much true purification does take place in a flowing stream, but this is not usually adequate, and towns and cities nowa- days are generally turning toward filtration, or other arti- ficial treatment on a large scale, of waters which for any reason are suspected of possible contamination. Some of these municipal purification works are elaborate and costly, as, for example, those in Albany, Philadelphia, St. Louis, Ithaca (New York), Lawrence (Massachusetts), Washington. 10. Public Gas Supplies and their Dangers. — There is no more danger from the products of combustion of illu- minating gas than from those of oil or other illuminating materials. The air of rooms naturally becomes heated and more or less vitiated by these products, just as it does by human breath or any other waste product of oxidation; but illuminating gas properly burned is no more danger- ous to life than is kerosene oil or any similar illuminant. PUBLIC SUPPLIES ple Unburned gas, on the other hand, escaping from pipes or fixtures is often extremely dangerous, both because it is poisonous and because in certain proportions it forms with air an explosive mixture. Illuminating gas is generally either “natural” gas drawn ready-made from the earth, or gas made from gasoline, oil, wood, coal, or coal and water, and hence known as “oil gas,” “wood gas,” “coal gas,” or “ water gas,” as the case may be. 11. Natural Gas consists chiefly of marsh gas, or methane (CH,), this making from ninety to ninety-seven per cent of the whole. It never contains more than one half of one per cent of carbonic oxide (CO), —a quantity too small to do serious damage. Though irrespirable, — that is, not fitted to support life, — natural gas is not poisonous. It may even leak into an apartment in considerable quanti- ties without endangering life or seriously damaging health. 12. Coal Gas is made by distilling “soft” or bituminous coal, and consists chiefly of hydrogen and marsh gas, with smaller amounts of carbonic oxide and other compounds of carbon. It contains from six to ten per cent of carbonic oxide, a highly poisonous gas, and cannot be admitted into living or sleeping rooms in any great quantity without ex- treme danger to life. It also readily forms explosive mix- tures with air. 13. Water Gas is made by passing steam over red-hot coal or coke (carbon), which decomposes the water vapor, pro- ducing, among other gases, an abundance of carbon monox- ide. As it leaves the generator, water gas burns with a pale blue flame only. For lighting purposes it is therefore ‘enriched by the addition of naphtha or other vapors which give it good illuminating qualities. But even after this treatment water gas generally contains from twenty-five to thirty per cent of carbonic oxide and is therefore ex- tremely poisonous. 516 THE HUMAN MECHANISM In cities supplied with water gas, cases of asphyxiation and death from gas poisoning are common. These come chiefly from ignorance (in blowing out the gas instead of shutting it off) or carelessness (in turning the gas on again after extinguishing the light), or from suicidal intent, or drunkenness, or from leaky fixtures, or from change of pressure, —a light turned low being extinguished by a decrease of pressure in the pipes and the gas escaping into the room afterwards when the pressure is renewed. The most remarkable (and often the most extensive) cases of poisoning by illuminating gas are those in which the inhabitants of houses or apartments not piped for gas have been poisoned by gas which has escaped from a broken or leaking main in an adjoining street. In these cases the gas makes its way underground to the base- ment of the house in question, and then, perhaps partly robbed of its warning odors by passage through the earth, rises through the house to sicken or kill those within. Whole families, and even groups of families, have occa- sionally been poisoned in this way, even in houses or tene- ments not piped for gas at all. The fact is that heated houses act like chimneys in producing a strong up-draft ; and in winter, when windows and doors are shut tight, this draft sucks in air from the surrounding ground. If the ground air happens to be charged with gas from a leaky main, both air and gas may enter the house and sicken or even kill the inmates, although the house itself is not supposed to receive any gas. It has been estimated that “fourteen per cent of the total product of gas plants leaks into the streets and houses of the cities supplied.” Headaches and malaise (a convenient term for “ feeling poorly”) may be caused by small and imperceptible leaks of illuminating gas, and great care should be taken to have all gas fitting well done, and all leaky joints or fix- tures made perfectly tight, especially if the gas used is PUBLIC SUPPLIES 517 water gas, now very generally supplied to the public in American cities. One of the great advantages of lighting houses by elec- tricity is that it does away with all possibility of gas poisoning except that from leaky mains in public streets, already referred to. The use of gas for heating and cooking requires especial caution, owing to the large quantities used and the tem- porary connections often employed (pp. 488 and 440). 14. The Purity of Public Milk Supplies. — Milk is one of the most universal and most important of foods. It is also one of the most peculiar, in that it is a secretion drawn directly from the bodies of living animals. This remark- able animal secretion, when fresh, is very sweet, smooth, and bland to the taste, but on exposure to the air generally spoils quickly and sours. It is obviously not the air alone which causes it to sour, for milk is easily kept sweet a long time if kept in a cold place, or if scalded when it threatens to turn sour. The spoiling and souring of milk are caused by certain bacterial microbes which, having got into the milk as it was drawn, or later from dust, air, dirt, or unclean pails or strainers, live and multiply enormously at the expense of the sugar and other food stuffs which milk contains. The so-called lactic-acid bacteria, in particular, thrive in milk, especially - if it is kept warm, and spoil it by converting the milk sugar (lactose) into milk acid (lactic acid). Milk that is pure should be free from dirt, and sweet rather than sour, but such milk is unfortunately not always easy to obtain, especially in cities. A black sediment in milk indicates dirt (usually cow dung), and so does a “cowy” taste. Milk may also be adulterated with water, with antiseptics, or with other substances, as has been shown above (p. 509) ; but the most serious impurity in public milk supplies is the occurrence of germs of contagious HS 518 THE HUMAN MECHANISM or infectious diseases. Many epidemics of typhoid fever and diphtheria have been conclusively traced to a public milk supply which served as the unsuspected vehicle of the disease. In all of these cases uncleanness of some sort —on the farm, in the dairy, among the milkmen, or else- where — is believed to have been always at the bottom of the trouble. Persons supplying milk to the public should take pains to keep their cows healthy and their cow stables clean; to milk only after careful washing of the hands, pails, cans, strainers, etc., and also only after washing the udders of the cow; and it should always be remembered that milk is a rich animal secretion which readily supports bacterial life and therefore should be scrupulously guarded against any invasion of dirt or disease. To secure rich, pure, clean, and fresh milk in cities, a higher price must probably be paid than has been the custom hitherto. The demand is for better, purer, cleaner milk; and for this it is reasonable to expect that more must be charged. It should also be remembered that the number of bacteria in milk, unlike that in water, does not depend simply on the number that get in, since germs multiply very rapidly in this rich food supply. Hence milk as soon as drawn should be chilled as far as possible before delivery. The mere souring of milk lessens its digestibility, especially in the case of infants, so that it is a matter of hygienic importance, particularly in warm weather, to lessen the growth of bacteria in it by immediate cooling as soon as drawn from the cow, and keeping as cold as possible afterwards. It must also be borne in mind that the milk-producing industry, while one of the oldest known to man, is still largely in a primitive condition. What is needed is a more scientific knowledge of the subject, more intelligence, skill, and cleanliness among those engaged in it, and, finally, PUBLIC SUPPLIES 519 expert supervision both on the part of the producer and of the sanitary authorities of cities. 15. Public Sewerage and the Disposal of Sewage. — One of the most beneficent procedures in any community is the establishment of a system of public drains which shall quickly and effectually remove all liquid and many solid wastes, especially the excreta of human beings and other animals. Well-built sewers not only do this but also carry off much “ ground ” water, making the soils of cities drier and therefore more wholesome. The term “sewerage” is applied both to the act of draining and to the system of sewers; the word “sewage,” to the contents of sewers. The disposal of the sewage of cities and towns is often a very serious, difficult, and costly problem. Sometimes the sewage can be safely emptied into a river, a lake, or the sea, but more often it is necessary to purify it, either upon land (where it may be made useful, though rarely profit- able, for agricultural purposes), or by chemical treatment, or by microbic (bacterial) action during cesspool or filtra- tion processes. The problem of the final disposal of sew- age is not yet fully solved, and at the present time is engaging the anxious attention of the world’s ablest sani- tary engineers.