I think anyone making a full and careful study of the records now obtainable of the effects of breathing sewer-air must come to a conclusion somewhat as follows: The danger from inhaling sewer-gas is in proportion to its concentration and poisonous composition. Where cesspools or very foul and ill-ventilated sewers are used, as is frequently the case in unprogressive, badly administered and ignorant communities, and very frequently in small towns and villages, the dangers may be very serious and constant, while where a well-ventilated and well-constructed sewerage system has been provided, as in the best administered large cities, the danger is comparatively small.

Fig. 38. Vented Pot becoming: an Unvented S Trap.

Fig. 38. Vented Pot becoming: an Unvented S Trap.

Nevertheless decomposing organic matter accumulates more or less along the soil and drain pipes of houses as they are usually constructed, even in the best sewered cities, and the products of such decomposition, if continuously breathed, in somewhat concentrated form, tend to produce a general impairment of the health predisposing the system to typhoid fever, and probably also to other infection, and lowering the vital forces of resistance to any form of specific disease.

As a preliminary to a better understanding of the subject it should be borne in mind that normal atmospheric air contains on an average, in 10,000 volumes, only about three volumes of carbonic acid, the oxygen and nitrogen standing in the relation of 2,090 to 7,910. If the carbonic acid increases to the amount of 50 to 100 volumes in the 10,000, it becomes fatal to human life, and with sulphuretted hydrogen 10 to 12 volumes in 10,000 becomes fatal. Yet these amounts are constantly exceeded in unventilated cesspools and foul sewers.

A choked sewer of Paris was found by Clanbry to contain 201 volumes of carbonic acid, and 299 volumes sulphuretted hydrogen in 10,000 volumes of air.

In another case he found 340 volumes of carbonic acid and 125 of sulphuretted hydrogen in a Paris sewer, and an average of 230 of carbonic acid and 81 of sulphuretted hydrogen in 19 cases.

Letheby found 53.2 volumes of carbonic acid in a London sewer; Miller an average of 10.6 in 18 cases and of 30.7 in 6 cases in London; Beetz an average of 31.4 in 8 Munich sewers; Laws an average of 69.2 in three London sewers, and 93.1 in another London sewer, even as late as 1892.

Cesspools are likely to be as bad or worse.

It goes without saying that the analysis of the air of most sewers of more recent date does not show such alarming amounts of poisonous gases and they should not show any dangerous amount at all, but instances of the kind do still occur, and, in the case of cesspools, dangerous foulness is very common.

Alessi says: "It is known that 18 cubic metres (yards approximately) of excremental matter can give out in 24 hours about 18 cubic metres of gas, of which 10 cubic metres are of fatty acids and hydro-carbons; from 5 to 6 cubic metres are carbonic acid; from 2 to 3 are of ammonia; 20 litres (quarts) of sulphuretted hydrogen. These gases, considered separately, constitute for man and animals the most poisonous substances, and their combination produces very rapid deleterious effects."

There is no excuse today, however, in the light of our knowledge of sewer and plumbing ventilation, for allowing these gases to accumulate in our sewers and drains in such concentration as to be injurious. Nevertheless foul cesspools and sewers still exist in the less enlightened parts of the country, and a few words are needed relative to the danger of breathing the products of decomposition in concentrated form.

Dr. Hankel,* in recording cases of injury from breathing cesspool air, has classified the effects into, (1), the mild form; (2), the fairly severe form; (3), the severe form, and (4), the chronic form. The first, he says, is well known among sewer men, the symptoms being the feeling of a heavy load upon the head and chest, and in worse cases, vomiting, severe pains in the abdomen, diarrohea, giddiness and weakness, with disturbance in the action of the heart and lungs.

*Ernst Hankel, "Ein Todesfall durch Einathmen von Cloaken-gas," 1895.

In the second form the skin becomes cold and covered with cold perspiration. Severe pains are felt in the stomach, throat and muscles. "Delirium, convulsive twitchings of the muscles, fainting fits, singing and talking, have frequently been observed at this stage." Then follow unconsciousness, convulsions, and other serious symptoms.

In the third, or severe form, death occurs. The workman, on entering the very foul cesspool "collapses all at once as if he had been struck by a bullet," the entrance being accompanied sometimes by severe convulsive fits, vomiting, foaming at the mouth, etc.

The chronic form has been observed in laborers in mines and chemical works, and is not applicable to plumbing.

Many cases have been reported, on good authority, of deaths through cesspool air poisoning of the severe form from very foul cesspools. They have occurred in places where the products of. decomposition and putrefaction were in a highly concentrated state, and under circumstances admitting of no doubt whatever as to their cause. They illustrate what may be termed the "direct" or "mephitic" (probably chemical) action of sewer gas, as distinguished from the "indirect" or "predisposing" action.

In addition to these practically demonstrated cases, we have the records of a different class of accidents resulting in death, which must be accepted as caused directly or indirectly by cesspool air, not with the positive proof of the first, but with sufficient evidence to leave no doubt in the minds of the physicians reporting them, or of the courts in several cases where they formed the subject of lawsuits. They are, in a certain sense, more interesting than the others, because they occurred under conditions more common, that is, under conditions in which the public as a whole are involved and not merely the comparatively small number who are obliged to work in the sewers.