(Concluded from last week.)

IN considering sewage by itself and not in the way it may affect our water supply, we find it in leeching cesspools, in earth-closets,in tight cesspools, and in the city sewers. The leeching cesspool stands in exactly the same relation to surrounding wells that the sewage discharged into a river does to the purity of the river. If we have a small enough supply of sewage and a great enough distance, we are safe. The earth-closet, when supplied with the proper kind of earth, is a sanitary appliance. The proper kind of earth is a dry loam, or surface garden soil dried without heat, which contains the forms of life that combat the noxious bacteria.

These disease-producing bacteria contained in the exposed sewage are not carried through the air.unless that sewage is first dried, desiccated, and then exposed to the wind. It is harmless so long as it is moist, and tests of the air in some large city sewers show a greater purity than the average wellventilated schoolroom when full of students. These organisms can be carried to us only by contact—the stench-producing organisms are not disease-producing; they are probably intended to keep us away from the foul matter in which they live. Sewer-gas itself, however unpleasant, is no more hurtful than any other gas which reduces the amount of oxygen; and it would be difficult to get a leak of sewer gas into a room from a well-ventilated system of plumbing that would vitiate the atmosphere anything like to the same extent as an ordinary gas burner, which uses during a giver, period at least as much oxygen as eight persons.

Dr. A, C, Abbott, of the laboratory of hygiene of the University of Pennsylvania,during the winter of 1894-95 conducted some experiments upon animals, as to the nature of sewer gas and of the gases arising from decomposing organic material. He took some rats, rabbits, and other animals, especial, ly subject to disease in laboratory experiment, and placed them in glass jars. Over some he passed a continuous stream of sewer gas; over others, gases from decomposing material. This was continued without interruption for five or six weeks, and none of the animals suffered a loss of appetite,nor seemed otherwise any the worse for wear. Disease-forming organisms are not gas-producers. The bacteria of decomposition almost universally produce gases. The parasitic bacteria seldom pro. duce gas. They live on our bodies and in the passages and chambers of our bodies that communicate with the external air. We have a variety which lives in our intestines, that is a gas-producer and which, if introduced into other portions of the body where bacteria do not normally belong, may produce disease. Hut, of the parasitic bacteria, a few are normally disease-producers, and of these normal disease-producers not one is known that produces gas. Even if they did, the gas would not of necessity be poisonous.

What is required of a sewerage system is to take away the noxious material as quickly as possible. Cesspools, therefore, are harmful, unless, tight; in which case the sewage being moist is harmless, though it gives off plenty of gas into the apartments above it. In the same way city sewers, if wellventilated, tight, and properly graded are all right. The only difficulty is where they shaii empty. A city like Buffalo, which has a river at its doors with a current of eight miles an hour, into which it can empty its sewage, and lake Erie from which to draw its water supply, can easily solve the problem. A small town can use the irrigation and sewage farm method. Where land is cheap the farm products will nearly pay the expense of running. This system depends for its success on the bacteria of decomposition,and other vegetation. The experiments of the Massachusetts board of health, already referred to, explain the principles of this system. The works at Freehold, N. J., are a good illustration of this type, The city sewers discharge into a large tank or basin. When this basin is full, the contained sewage is allowed to flow with full head through one of the distributing systems—there being six different fields used in alternation. The discharged sewage, before flowing on to the fields, first flows through a barrier of broken stone, where the algoid vegetation does its destructive work. The alternation of the fields gives this vegetation time to develop—being swamped with food—and the several days’ exposure to the sunlight between the floodings destroys the noxious bacteria that may have escaped the barriers of broken stone.

With respect to house filters—The old charcoal, or a sand filter, might do, if used only one day in four or five, and ex-

posed to air and light during the intermediate days. The wire filtersthat screw on the faucet and reverse are an abomination; the retained bacteria have time to multiply,and are then slowly set free when the filter is reversed, and, after a time, the water passing through in either direction will contain more bacteria than is contained in the same amount of water in the pipe supplying the filter. A pressure filter containing a film of paper pulp to be removed daily might be very effective. As to the earthenware filters—These answer their purpose,if they are sterilized by heat about once in four days. It has been shown by experiment that after this period there are more bacteria contained in the filtrate than in the water that enters the filter. The explanation is that it takes about four days for the bacteria to grow through the pores of the eathenware, and, after this is accomplished, these earthenware walls become a breeding-place. If, however, one removes the earthenware portion and either lays it on the coals till raised to a red heat, or puts it in a steam chamber far half an hour, and repeats this operation every fourth day.the filter will then be perfectly safe. It stands to reason, however, that every city should furnish water that is perfectly safe for all to drink —water properly filtered.



CLARENCE O. AREY, C. E., M. D., recently deceased, in a paper read at Cleveland, Ohio, on the subject of “Water Supply and Sewerage as Affected by the Lower Vegetable Organisms,” considers first the nature and lifework of these minute organisms which are found everywhere and then establishes their place in the circle of the varied forms of animal and vegetable life.

Man, he points out, lives on animal and vegetable food— the animals themselves chiefly living on herbs and vegetables; this vegetable life in its turn depending upon the gases in the air and in the soil in which it is developed. Water is part of the food of all life, and it is not necessary to consider it in differentiating the various forms.

The life-work of the lowest forms of vegetation—the bacteria, the yeasts, and the moulds—is to supply the gases on which the higher forms of vegetable life depend. They feed on dead organic matter, reducing it to its original elements, which are chiefly gases. Without them, unless destroyed by fire, or cauterized by chemicals—mummified—all such dead matter would remain forever in the exact condition in which it was when death took place.

These bacteria are the lowest forms of vegetable life known. They consist of single cells; their function, as a class, being to reduce dead matter to its original elements, though some are parasitic and live upon other forms of life. Of those that are parasitic in their nature, certain ones eliminate a poison which is deadly to the person or animal upon which they happen to find an abiding-place. These produce disease as follows: All life requires food: all life gives off excretions. All bacteria absorb food; all bacteria excrete other matter. The comparatively few disease producing bacteria excrete poisons more deadly quantitatively than any other known chemical poisons. These poisons separated from the bacteria will produce the same disease as the bacteria themselves, but do so more quickly, because the living bacteria require time to multiply until they are numerous enough to produce a poisonous quantity of their excretions before the symptoms of disease show themselves. These same poisons diluted sufficiently, as in drinking water, may after a time render the person drinking the water incapable of taking the disease they produce when given in poisonous quantities. The poisonproducing bacteria are the ones that we wish to keep out of our water supply, out of our houses, and out of our sewers.

Yeast*, again, are slightly larger organisms and contain a nucleus. They are generally gas-producers. Moulds, on the other hand, are slightly higher up in the vegetable scale, as they branch and have fruit. Each of these last is, perhaps, antagonistic to the bacteria; but the greatest enemy of bacteria is sunlight, which kills their growth.

In taking up the subject of water supply, let a river town be first considered. Suppose this town located on, and taking it* supply from a river, ten miles above which is a small town discharging its sewage into the river. Whether the health of the lower town will be good or bad depends upon the amount of sewerage discharged by the upper town in proportion to the distance between the towns and the size of the river—to put it concisely, on the effect of the disease-producing bacteria that are carried in sewerage.

The sewage, when small in quantity, is discharged into the river and is immediately diluted with the river water. It is tumbled over and exposed to the sun, and at every tumble thousands of bacteria are destroyed. The bacteria are filtered through the green slime growing in the rivers, going to meet their death in the filtration, till at the end of three or four miles the water upon examination is found to be pure enough for drinking purposes. But, if the sewage is once allowed in the river, there is no limit to its quantity, and it soon gets beyond the power of the combating agencies of Nature. As to the length of time that bacteria will live in water when in contact with the combating agencies the data are not exact. In some experiments they have died out in a few days from the time of their introduction into the water, while in others they have persisted for several weeks. But, on the whole, it is safe to say, that, if all source of infection is cut off from a body of water, it will entirely purify itself of disease-organisms inside of a few monthts.

In the investigations of the Massachusetts board of health which were carried on a few years ago. it was found that, if given quantities of sewage were discharged through open beds of gravel at regular intervals, as many bacteria were found in the filtrate at the first discharge as in the waste matter discharged in the gravel bed. After the gravel bed had been in use some time, however, with the proper intervals between discharges, it was found that the filtrate running away from the gravel beds was free from a harmful percentage of bacteria. Upon investigation this was explained in the following manner: When the sewerage was first discharged through the gravel, the gravel was clean and no forms of life that are at war with the bacteria were present. During the intervals, the food for the warring elements being present, their seed became planted there and grew, thriving upon the bacteria and other material furnished by the discharges.

This applies directly to the water supply of all large cities where filter beds are used. Take a freshly made filter bed,and the water comes through impure. After a little time algoid vegetation—the green slime—begins to grow at the bottom of the water and on the sides of the filter beds. As this accumulates, the bacteria are retarded in the meshes of this fine vegetation, which in some way destroys the bacteria. Finally the meshes become so fine that even the water does not percolate. Then the bed must be cleaned; but no new filter bed, nor freshly cleaned one should be used to supply a city with drinking water.

In the city of Berlin, some years since a portion of the city supplied with a certain filter bed became short of water. The level of the water was raised two feet in this bed, to give a greater pressure and force mote water through the filter. The result was an immediate outbreak of typhoid fever in that part of the city supplied by this particular filter bed, and in no other part of the city. The most plausible explanation is, of course, that these bacteria had been accumulated in large quantities in the meshes of the vegetation growing on the surface of the filter, and that the sudden heavy pressure had forced them through the filter before there had been time for them to meet their death at the hands of their natural enemies.

In the new water works of Berlin, besides the usual corps of engineers, there are two bacteriological laboratories located at two different points of supply. Dr. Proskauer, who has charge of these laboratories, was the first one to show that it was not the sand alone, but the algoid vegetation on its surface that formed the filter arresting the bacteria and in some way absorbing or removing the dissolved organic matter. After the beds have been cleaned, the filtrate for the first fortyeight hours is rejected. There are in this system twenty-two filter beds, of which only sixteen are in use at one time, while the remainder are being cleansed. To avoid all possible cause of error from any flaw in the filter bed, the filtrate is examined daily in the bacteriological laboratories. Koch’s three rules regarding fil ration are rigidly enforced. These are:

  1. That the rate of filtration shall never exceed ioo mm. per hour.
  2. That the filtrate of each basin shall be examined daily while in use.
  3. That the filtered water containing more than 100 bacteria to the c.cm. shall be rejected or pumped back into the unfiltered reservoir.

The average number in the water as now supplied to Berlin seldom amounts to fifty bacteria to the c. cm. The unfiltered Tegel water averages about 200,while the former source of supply in the Spree contained from 10,000 to 100,000 or more to the c.cm. A filter conducted on these principles should reduce the bacteria in a water that is badly contaminated in the ratio of 1,000 to I.

(To be continued.)