for ornament or luxury; it varies greatly according to the style of house, the essential point being that it shall furnish the means of getting rid of excreta and of water fouled by domestic use, without danger to the health of the inmates of the house.
What, then, are the dangers to health from defective plumbing? They are due to gases or to micro-organisms coming from defective fixtures, joints, or pipe, or from soil pollution due to such defects. The gases in question are, for the most part, products of the decomposition of organic matter of animal origin, and the types are carbonic acid, ammonia and its compounds, and sulphureted hydrogen. There are also produced certain effluvia, of the precise nature of which little is known; the most common is that giving a faint, sweetish, peculiar odor, resembling that of boiled turnips.
These gases and odors do not produce specific disease, but when they are distinctly present in a house the inmates are liable to be affected with various forms of disturbed digestion, loss of appetite, slight headache, and a depressed state of vitality. How far these are due to the gases themselves and how far to the micro-organisms present under such circumstances we do not yet know. The majority of persons gradually become so accustomed to their effects that they can live and work with little or no apparent inconvenience in an atmosphere which is so charged with them as to be not only offensive, but really dangerous to those accustomed to pure air only. Plumbers, scavengers, workers in sewers and at sewage-works, or in bone-boiling establishments, etc., prove this; but it must be remembered that these are survivors, and that a certain number who begin these occupations soon find it necessary to go into some other business. Upon the whole, the dangers from gases only in connection with house-drainage are small, and comparatively easy to avoid, the main thing for this purpose being a complete and constant ventilation of the pipes.
In part the dangers are due to extremely minute particles of living matter, most if not all of which are vegetable organisms known as bacteria. There are many different kinds of bacteria, and they have very different properties and powers, but those which concern us in this connection are those which grow and multiply in decomposing organic matters, and especially in excreta. Almost without exception these bacteria belong to species which are found in the air of streets, in all intestinal discharges, and in all putrefying matters; they are not only harmless under all ordinary circumstances, but are highly useful in decomposing dead organic matter into simple compounds available for the nutrition of plants. They are found in countless numbers in the slimy, pulpy layer of decomposing matter lining the interior
