The defensive proteid or lexins, in which upon this theory these qualities reside, appear to be ferment-like albuminous bodies, which in the absence of other physiological tests, Mr. Hankin proposes to divide into two provisional classes-sozins, phylaxins. A sozin is a defensive proteid that occurs naturally in a normal animal. They have been found in all animals yet examined. A phylaxin (to guard) is a defensive proteid only found in an animal artificially made immune, and which, so far as known, only acts on one kind of microbe or its products. Each may be sub-divided into those that act on the microbe itself and those that act on the poison it generates, to be called myco (fungus) and toxo (poison) sozins and phylaxins.

As these may also be obtained from cells, they do not exclude the phagocyte theory. Metchnikoff, of Paris, and Hankin, of Cambridge, are the respective exponents of the phagocyte and defensive proteid doctrines. It is probably the case, as Emmerict remarked, that no general theory of immunity can be formulated now. Phagocytosis can be demonstrated beyond a doubt under the microscope, and the experimental work with blood serum seems to show that other factors than the amoeboid operates to induce protection. It is reasonable to suppose that both the cell and the serum play important parts and that the chemical element is not yet made out.

Belonging to this last factor are Klein and Coxwell's experiments on the influence of chloroform upon immunity. Frogs and rats are ordinarily immune against anthrax; but when inocculated with it. under chloroform or ether, both of these invariably die, although, so far as the microscope shows, the leucocytes continue to swallow the bacteria. This seems to show that the chemical changes may be established in the blood sufficient to neutralize the destructive power of the leucocytes.

SELF PURIFICATION OF RUNNING WATER.

The pages of the MONTHLY BULLETIN of this Board have not infrequently presented statements in relation to the self purification of polluted water, such statements having been derived from the results of experiments and investigations made by parties eminent in scientific work of that kind as well as in other lines, and also results of examinations of different waters in Rhode Island in the chemical laboratory of Brown University, and by the investigations of the Secretary of the Board.

In the pages of this annual report of the State Board of Health, the quality of the waters of the Pawtuxet river at different points, and at the faucets in Providence city, will be shown as ascertained by Prof. J. H. Appleton, and State Assayer G. E. Perkins.

As pertirent to the subject of self purification of river waters, the following paper is presented. It was published in Le Journal d' Hygiene, and translated for the Marine Hospital Bureau, Washington, D. C., and republished in the Abstract of Sanitary Reports of that Bureau.

"A recent issue of the Annals of Experimental Hygiene at Rome contains a paper by Dr. Alessandro Serafini on the spontaneous and rapid purification of running water from all deposits received during its passage through the centres of population. Dr. Serafini's observations appear to be in direct agreement with those recorded by the Royal Commission of London and the report made on the purification of the Seine; also with the chemical and bacteriological analyses made by Schelhaas of the water of the Isar, by Fleck of the Elbe, and by Celli and Scalla of the Tiber. They show that the quantity of organic matter, ammonia and bacteria, carried along by the water diminishes at a short distance from the point at which they are discharged into the stream, while the proportion of products which indicate the process of oxydation, viz. nitrous and nitric acid, increases. The following is a summary of the conclusions drawn by Dr. Serafini from his experimental studies:

1. Aeration by continuously renewed contact with the air does not prevent the development of micro-organisms in running water, and it is not, per se, suffi

cient to accelerate the process of oxydation. Experiment shows that there is no appreciable and constant difference between water in which aeration is constantly renewed by the motion of the current and that in which aeration occurs under the influence of temperature or barometric pressure.

2. The transformation of organic matter takes place so slowly in water that it is extremely difficult to follow the process, either in the general flow of the stream or in any section of it which is made the subject of special analyses. While there is no doubt that nitrification is due to the bacteria in the water, some time must elapse before the process can be recognized, whether the water be flowing or stagnant, deep or shallow.

Light retards the transformation of organic matter by destroying the bacteria which are the essential factors of oxydation.

3. A temperature of 0° or -6° incontestably destroys great numbers of the bacteria and arrests the development of those which survive. For this reason water contains the minimum number of bacteria in winter.

4. In great masses of water a lowering of the temperature of the surrounding atmosphere does not necessarily exercise a destructive influence on micro-organisms. This explains the fact, observed in experimental research and in local observation of streams of rapid as well as sluggish current, that a gradual and continuous deposit of bacteria takes place.

5. The rapid diminution of the bacteria discharged into rivers from the sewers of cities is not due to oxydation occurring in the body of water, but to concurrence of several factors, viz: Sedimentation, dilution, the mechanical action of substances which are first held in suspension in the water, and then deposited, the movement and disturbance of the water, low temperature, the superficial filtration which takes place in the bed of the stream, and finally some inherent action of the water itself.

Purification from organic matter and the intermediate products of decompo sition, is probably due to sedimentation and the slow and continuous oxydation occurring in the bed of the river. Water flowing over the river bottom dissolves the nitrites and nitrates formed in the zone in which sedimentation takes place. Sedimentation and dilution cause the rapid diminution of organic matter and ammonia, and solution facilitates the liberation of the nitrates and nitrites, the result of this double process being the purification of the water."

In addition to the above and as pertinent thereto may be presented a brief synopsis of a paper by Dr. Percy F. Frankland-an eminent authority-on "The Present State of Our Knowledge Concerning the Self Purification of Rivers," read at the International Congress of Hygiene at London in 1891.

'We have evidently placed too much confidence in the innate power of rivers to throw off the evil effects of pollution by sewage. On the other hand we find, if we may believe the authorities, some comfort in the fact that the bogey of the present day, the microbe, has not that miraculous vitality which popular belief bas attributed to it, and is even to be disposed of by so commonplace a matter as sedimentation."

Dr. Frankland, in the course of his paper, refers more than once to the remarkable powers of self purification of the Thames. That our metropolitan river must practice this virtue to a prominent degree is manifest from the cruel ill-usage to which we subject it; but we gather that the author referred chiefly to the up-country reaches. Below-bridge, especially in the neighborhood of Barking and Erith reaches, no self purification could compensate for the filthy flood that is daily discharged at Crossness.

There have been reports of various highly-paid experts from time to time, the reading of which would lead one to suppose that there was nothing or little to be desired in regard to the state of the water in this region. But those who live near the banks, or whose duty takes them down the river, know how misleading these reports are. At low water especially, the banks are formed by reeking flats of sewage disposal.

Dr. Frankland's paper says nothing about the unsavory reaches below bridge, but commences by saying that the subject of the self purification of rivers admits of being considered from two perfectly distinct points of view, viz., from the chemical and biological aspects. Until recently the subject has only been

discussed from the chemical point of view. The firm conviction possessed by many that rivers undergo spontaneous purification in the course of their flow is generally based upon personal observations made upon streams, in which the process appears to be going on in such a striking manner that no analytical evidence is required. All engineers are acquainted with streams which are visibly polluted at one spot, and apparently pure a few miles lower down. When such cases are further submitted to analytical tests the latter, of course, fully confirm the previous ocular impressions. In fact, such disappearance of organic matter does take place; but when these cases of supposed self purification are carefully investigated, it becomes doubtful whether the phenomenon is due to much beyond dilution and sedimentation. The careful experiments which have been made to test this point are by no means

numerous

A series of investigations was made by the Rivers Pollution Commissioners of 1868 to test the point, both as regards highly-polluted streams and comparatively pure ones; but in both cases their results were of a negative character, and pointed to no real purifications, i e., destruction of organic matter, although there was distinct evidence of considerable improvement in the quality of the water through sedimentation.

Some years ago the author undertook a series of experiments to further test this point in connection with the Thames, which has always been regarded by some as a river possessed of most remarkable self purifiying power, and which, undoubtedly, often does reach London after a long flow through a cultivated and fairly populated district in a surprisingly pure state. The experiments in question consisted in taking samples of the water flowing in the river at differ ent points on the same day, with a view to establishing whether on the whole the chemical quality of the water was improved or deteriorated during the course of its long flow. Thus, on one day, samples were taken at Oxford, Reading, Windsor and Hampton; on another day at Chertsey and at Hampton, and on three different occasions samples were collected both at Windsor and at Hamp

ton on the same day. The results of analysis on these various samples clearly indicate that the chemical quality of the water undergoes slight but almost continuous deterioration in flowing from Oxford to Hampton. This deterioration is in spite of a large increase in the volume of the water, a large proportion of which gains access to the river from springs in the chalk, and is of very high purity.

The author continues by saying that of the most recent investigations, we are led to the conclusion that sedimentation is the main cause of self purification in river water; of any rapid oxidation of dissolved organic matter there is still no reliable evidence, although of course dilution, which frequently takes place on the largest scale, as in the case of the Thames, without being suspected until made the subject of a most careful scrutiny, will produce a superficial appearance of such a result.

The removal of microbes by sedimentation during the flow of a river is unquestionably of great hygienic importance, and of much greater hygienic importance than the alleged oxidation of dissolved organic matter, which in itself can have no power of communicating zymotic disease; it is, however, a process which cannot be relied upon as furnishing any guarantee that harmful microbes, turned into a stream at a given point, will no longer be present in the water at any point lower down. From the numerous experiments which have been made on the vitality of pathogenic microbes in water, there can be no doubt that many forms which might have subsided would remain alive for long periods of time, and be carried down uninjured when the river was next in flood.

The author concludes his paper by saying that we must not allow sedimentation of microbes to cause us to relax our protective measures to exclude contamination from our streams, but on the contrary, bacteriological research clearly indicates on the one hand the value and importance of purifying by the very best available means all dangerous liquids, such as sewage, before admission into rivers, and, on the other hand, to submit the water drawn from streams for town supply to the most careful subsidence and filtration through sand be fore delivery.