In England the flashing-point of mineral oils has been fixed at 73° Fahr. The material of which the reservoirs of lamps are composed should not be glass or other breakable material, and the wick should be contained in a small wick chamber extending nearly to the bottom of the reservoir. Only a tight fitting wick must be used.
The best illuminant for domestic purposes is incandescent electricity, in which no products of combustion are formed, and only a comparative small amount of heat is produced. Electrical illumination possesses the further advantages that there is no blackening of ceilings and no damaging of other decorations as in illumination by gas.
(3) Air Rendered Impure by Exhalations from the Sick. In addition to the ordinary impurities of occupied rooms, special impurities are produced, varying with the character of the disease. They may include infectious particles from the sick. In wards for consumptives and for diphtheria, dust in the room has been found to contain the special microbes of these diseases. Making beds, sweeping floors, &c. may help to scatter infectious dust; hence the importance of adopting means of cleansing which will not scatter dust, and of keeping sick-rooms spotlessly clean. In many diseases e.g. consumption, a patient may re-infect himself with such infectious dust, and thus diminish his own chance of recovery (see page [311]). Hospital wards can scarcely be too freely ventilated; but even more important than ventilation is the strictest cleanliness in every minute detail.
(4) The Air of Sewers, Cesspools, etc., may contain the products of decomposition of sewage, such as volatile fœtid organic matter, carbo-ammoniacal substances, sulphuretted hydrogen, carbonic acid, etc. The amount of these various products varies greatly under different circumstances, such as dilution of the sewage, ventilation of sewers, temperature, etc. The effluvia from cesspools are usually more concentrated than those from sewers. It appears fairly certain that the emanations from sewers or drains may give rise to diarrhœa and gastric disturbances, and to certain forms of sore throat, which favour the production of diphtheria. On the other hand, there is much evidence showing that the danger from sewer-emanations has been exaggerated. Carnelley and Haldane found that the air of the sewers of the Houses of Parliament and of certain sewers of Dundee was not very impure, containing a smaller number of bacteria than external air. There is reason to believe that the emanations from well-ventilated sewers, possessing a good gradient, so that the contents of the sewers are hurried away to the outfall, are free from danger. The chief source of possible danger would be the escape of the bacteria of such diseases as enteric fever or diphtheria, which had been discharged into the sewer from patients suffering from these diseases. But, in the absence of splashing, these bacteria could not escape from a liquid medium. Their escape could only occur when the sewer became dry, and the dust was carried up by rapid currents of air, a very improbable occurrence in sewers. Hence in the majority of instances sewer emanations must be freed from the accusation of producing infectious diseases. Sewer-men usually enjoy good health, and there is no excess of infectious diseases among them.
The emanations from obstructed drains or sewers may cause serious mischief, similarly to that occasionally produced by the emanations from cesspools. Under such conditions, sulphuretted hydrogen, carburetted hydrogen, and other gases are evolved, and fatal asphyxia has been caused by these. In other instances acute sewer-gas poisoning, without pneumonia, has followed.
The exhalations from cesspools or privies while cleaning them out, may produce severe disorders, which are sometimes fatal. When a drain is newly opened or sewer gas gets into a house, a less marked form of poisoning sometimes occurs, chiefly characterised by languor, headache, vomiting, and diarrhœa. In some cases there may be febrile attacks lasting a few days. Children are especially sensitive to such conditions and quickly fall into ill health.
The direct origin of acute infectious diseases from the effluvia from drains or cesspools has occasionally occurred. Leaky and choked drains under a house are especially dangerous. The subsoil becomes contaminated more and more as time goes on; foul gases are aspirated into the house, owing to its interior being warmer than the subsoil; and finally infectious matter may find its way into the house, or carried by insects or vermin, through cracks in the earth.
Diphtheria has been ascribed to emanations from drains and sewers. There is reason to believe that a non-specific form of sore throat may originate in this way; but diphtheria is generally, if not always, spread by personal infection. Diarrhœa has been occasionally ascribed to sewer-emanations. It chiefly occurs in hot weather, and is usually associated with a foul condition of the surface soil, and speedily ceases after this has been scoured by copious rain.
Enteric or typhoid fever, has been frequently ascribed to drain and sewer effluvia. It was formerly thought that putrefactive changes alone, under certain conditions of temperature, etc., would produce it, and Dr. Murchison, one of the greatest authorities on the subject, who adopted this view, proposed for enteric fever the name “pythogenic fever” (i.e. filth-produced). Isolated cases of enteric fever, occurring where there is no system of drainage, support the same view, as does also the fact that, with the adoption of drainage, the enteric mortality has steadily diminished. On the other hand, numerous cases can be quoted to show that emanations from excreta have been breathed, and sewage-contaminated water drunk, for years, without the production of a single case of enteric fever—until a case is accidentally imported. The weight of evidence is clearly on the side of the view that only emanations from the liquid or solid dejecta of previous enteric patients will produce enteric fever, and that it is the solid particles of the urine or fæces, either inhaled as dust or carried on to food by flies, &c., or mixed with food by contaminated water, &c., which cause infection. Furthermore, modern investigation shows that infection by dust is the exception in England; and that the enteric infection is usually swallowed and not inhaled, being taken in infected water or milk or other food.
(5) Effluvia from Decomposing Organic Matter.—(a) The air of marshes contains an excess of carbonic acid, marsh gas, etc., in addition to other organic matters. Malarial diseases are commonly ascribed to the inhalation of the marsh effluvia under certain conditions, though the recent proof of the part played by the mosquito in spreading malaria, puts the inhalation of such effluvia in the background as cause of this disease (page [307]). Some forms of diarrhœa and dysentery have been ascribed, with a less degree of probability, to the same cause. In this case, as in that of emanations from other organic sources, the impurities received by the air are both gaseous and particulate.