Professor Nichols analyzed the air of the Berkeley Street sewer in Boston, a type of a badly-constructed and badly-ventilated sewer. The sulphureted hydrogen, etc., were in too small quantity to be measured. The highest percentages found were, of oxygen, 20.90; of nitrogen, 79.26; of carbonic acid, .4 (40 parts in 10,000). The lowest were, oxygen, 20.48; nitrogen, 78.89; and carbonic acid, .05 (5 parts in 10,000).
Letheby found that sewer-water (containing 128.8 grains of organic matter to the gallon) excluded from air yielded, for nine weeks, 1.2 cubic inches of gas per hour. In one hundred volumes of this mixture there were 78.83 parts of marsh-gas (carbureted hydrogen), 15.90 parts of carbonic acid, 10.19 parts of nitrogen, and .08 of sulphureted hydrogen. Examination of sewage-mud in the Seine by Durand-Claye gave 72.88 parts of marsh-gas, 13.30 of carbonic acid, 6.70 of sulphureted hydrogen, 2.54 of carbonic oxide, 4.58 of nitrogen, and some other gases. Such mixtures are sometimes found in long-closed cesspools and privy-vaults, but not in sewers proper.
Of these gases, sulphureted hydrogen and carbonic acid are very poisonous, and when they are inhaled in concentrated form produce almost immediate unconsciousness, and often death. When less concentrated, sewer-air may cause nausea and vomiting, followed by a low fever which sometimes kills, and, if not, results in a tedious convalescence. As a rule, it is so largely diluted that it produces no immediate effects, excepting the discomfort due to offensive odor, and the mental anxiety resulting therefrom.
The effects usually attributed to the continued breathing of diluted sewer-air are general malaise, loss of appetite, anæmia, impaired nutrition, and therefore diminished power of resistance to attacks of disease which are not directly attributable to sewer-air poisoning. It is doubtful whether these effects are due to the constant introduction of sewer-air in minute quantities into the blood, or to the inhalation of particles of organic matter floating in such a contaminated atmosphere.
The greatest danger, however, in the breathing of sewer-air is that of inhaling with it the living particles (bacilli, etc.) contained or developed in the excreta of diseased persons.
The diseases believed to be propagated in this way are cholera, typhoid fever, and dysentery. The discharges both from the mouth (stomach) and bowels are known to be poisonous.
It is believed by many that the poisons of typhoid fever and diphtheria may be developed de novo by the decomposition of the mixtures found in cesspools and sewers.
There also seems to be a connection, imperfectly understood, between bad drainage and malarial fevers, and perhaps cerebro-spinal meningitis.
The origin of yellow fever is not yet ascertained.
Surgical erysipelas, puerperal fever, and hospital gangrene, are only developed on and about wounded surfaces, and seem to be due to the organisms developed in the secretions of such surfaces, where ventilation and drainage are bad.