*Carbonic or carbonous oxid according to the older terminology.

Therefore the dangerous element in sewer air must be sought in what is called organic vapor, which is an indefinite name for something of which no definite knowledge has so far been attained. The very recent researches of Dr. Alessr† corroborate this conclusion.

In spite of the very general testimony of modern authorities as to the reality of the dangers of breathing certain kinds of sewer-air in confined places, there have been misbelievers who have characterized the wide-spread fear of sewer-gas as groundless panic, and the records of the great epidemics as mere sensational stories. Therefore it is necessary to follow and fully understand the recent very important investigations and discoveries of scientists in this domain, not only as an aid to personal security, but also because they have a very important bearing upon the methods of sewerage and plumbing, which should be adopted to conform to the new light they have shed.

It was very natural that, before the science of bacteriology had enlightened us, sewer-gas should be regarded with a very great and vague terror as of an unknown enemy awaiting us in the dark.

So we find exaggerated fears on the one hand and a false sense of security on the other, both based on an ignorance of the nature of sewer-gas, and of the proper method of dealing with it.

On the part of the terrorists it was common to hear the air of even well ventilated sewers described as a form of concentrated pestilence laid on our houses with the soil pipe †G. Alessi "On Putrid Gases, as Predisposing Causes of Typhoid Fever Infection," Journal of the Sanitary Institute, London, 1895 connections as one would connect a fuse to explode a mine. Doctors and sanitarians seemed to vie with one another in arousing the greatest possible amount of alarm. A physician quotes a professor of hygiene as saying, "Sewer-gas is so subtle that its presence is many times not detected, and yet so laden with the germs of disease that diphtheria, scarlet fever, typhoid fever, and other fatal maladies are the sure event to those who dwell in such air-poisoned houses." Indeed, it might almost be said that about every disease or indisposition to be found in the medical calendar has been at one time or another attributed to sewer-gas poisoning.

On the other hand, the scoffers pointed to the experiments of Carmichael, Wernich, Miquel and others, and declared that disease germs could no more escape from sewage than a sausage could jump out of a kettle of water, and that the fear of sewer-air was altogether irrational. The plumber, they said, is a sufficient refutation of "their notions," for he works at the very jaws of the sewers and flourishes on their breath. They seemed to ignore the fact that plumbers do suffer, when exposed to foul gases, and that the most prudent of them take the precaution to keep the "jaws of the sewers" well gagged while they are at work upon them. It is their custom to complete the plumbing work before the sewer connection is made, so that sewer-gas is not allowed to play about the building with such unrestrained license as many seem to imagine. But, as compared with workers in other trades and professions, plumbers lead an out-of-door life largely in buildings but partly completed or closed in, and must be in the full vigor of youth to carry on to the best advantage their somewhat arduous calling, and the experiments of Alessi show that the system undoubtedly becomes inured to some extent to inhaling the products of decomposition.

These factors enable them to withstand the enervating effects of exposure to sewer-air better than others, and so far as the pathogenic bacteria are concerned, it is in the feeble body, debilitated by confinement and impure air that they make most headway when once they gain entrance, against the armies of the white corpuscles or "Leuco-phytes" with which nature has so wonderfully provided us as a body guard.

But Dr. F. L. Dibble,* of Philadelphia, has made the most vigorous protest against the reign of sewer-gas terror in his "Vagaries of Sanitary Science." His writings, however, like those of his more violent adversaries, were published more than fifteen years ago when his peculiar deductions were more excusable than they would be today. He writes as follows: "It was soon after 1850 when the gases of the sewers first began to be talked about; but it was not until about the year 1857 that it was decided, not by chemical experiment or by any other investigation, but by a whim of the sanitarians, that there should be a distinct substance known as sewer-gas.

"The most discordant and contradictory properties were at once imputed to it. Sometimes its gravity caused it to descend into the bowels of the earth; again, by its surpassing levity, is ascended to heaven. Its powers of lateral diffusion were illimitable; it would permeate masonary eight feet thick; its backward pressure was enormous; then, unlike other gases, instead of finding vent at the manholes and large openings of the sewers, it had such affinity for the human system, to poison and destroy it, that it remained pent up until it could find egress through some crack or pin-hole, and escape into our dwellings. Sometimes it had a vile odor; again it had a faint, mawkish smell. but the climax of danger was reached when it was odorless, 'Poisoning by sewer-gas,' says the London Lancet of 1882, in condemnation of the water carriage system, which has no smell, is the cause of many maladies. We take the rattle off the tail of the snake that he may better bite us with impunity. Better let the atmosphere of a house be nauseating from the fumes of recent faeces or pestilential from the fumes of a cesspool than poison its inhabitants with the demon sewer-gas skilfully laid on by a system of closed drains' Ventilating them by gratings in the street 'is Machiavelian in its refinement of folly and wickedness.' "