Proceedings of the west of England and South Wales branch of the incorporated society of medical officers of health

PROCEEDINGS

OF WEST

OF ENGLAND

t i n g h a m e n d e a v o u r e d t o obviate c o m p l a i n t s by t h e e r e c t i o n of h i g h ventilators in a d d i t i o n to t h e i r street g r a t i n g s ; C o v e n t r y relied u p o n rain-water spouts a n d factory c h i m n e y s , etc., etc. W a s it n o t possible to arrive at the following c o n c l u s i o n s : T h a t t h e c o m p l a i n t s of e m a n a t i o n s were e n t i r e l y due to t h e system o f placing grids in t h e roadway ; t h a t this system was n o t a n a b s o l u t e necessity for sewer v e n t i l a t i o n ; a n d t h a t systems of high ventilation were sufficient to k e e p sewer air w i t h o u t u n d u e pressure. Allusion was also m a d e to H o l m a n ' s gas c o l u m n s , C a i n k ' s sewer gas filters, a n d a recent improvement upon Holman's patent by Deakin, of B i r m i n g h a m , Dr. BOOBBYEP,- continued the discussion, and said with regard to Nottingham, which had been mentioned, high ventilators were erected on his recommendation, but he had little faith in their powers of ventilating a length of sewer ; even when square and of considerable size, the anemometer failed to act after 12 feet above ground-level. Nottingham possessed gradients which obviated many complaints, but in his opinion a free outlet in the roadway was absolutely necessary to prevent over-pressure. Hehad known manhole lids to be forced off by the wind, and thought it likely that house-traps would be forced also. With regard to the emanations themselves, it had been shown by Mr. Parry Laws that sewer gas was innocuous as far as miero-orgamsms were concerned, but was only dangerous chemically ; if this was true of London sewers it would apply anywhere. No high ventilation acted over any distance ; e.g., in Brighton, where furnace extraction was tried, there was no air movement in the sewer after the first quarter of a mile. Dr, ALFRED HILL remarked that, as Dr, Boobbyer's last records proved, sewers not being alr-tight were never really unventilated. He was disappointed not to find any practical suggestion by D n Manley. A good gradient produced a perfect scour, and well.scoured sewers in which no deposit remained needed no ventilation. He did not believe in the principle that every house should contribute to the ventilation el the sewer, and so have to put up with their nelghbours' stinks as well as their own. His experience of Itolman's coIumns was that they were expensive without being efficient, while factory chimneys were limited in number and irregular in operation. Road ventilation had never been proved to produce zymotic disease, in spite of allegations to that effect, and many of the complaints were due to sentimental objections. The true cure was an improved form of sewer in which the sewage did not lie and generate gases, which, once generated, no system of ventilation could remove. Dr. MAY concurred with the last speaker, and alluded to flushing as a valuable preventive. Much of the success of Boarnemouth was due to their regular and efficient system of flushing with sea-water. Dr. BOSTOCK HILL followed on the same lines, and said that the only true remedy in towns was flushing, and not ventilation. Sewers when first laid were too large for their requiIements, and the mere trickle of sewage never scoured them ; gas was produced, and an outcry leading to the use of high ventilators, in which he had no faith. He did not believe that sewer gas produced zymotic disease, though it was, no doubt, offensive. From the statements made by the promoters of patdnt ventilators it was clear that sewers were not airtight, while they proved a great deal too much. He did not believe that sewer gas could increase the luminosity of a gas jet, nor that a single gas lamp would influence the air over 45o yards of sewer. Dr. MANLEY briefly replied to the effect that he was still of opinion that grids in the roadway were a nuisance and unnecessary ; without being the cause of zymotic disease, they were quite capable ot producing nausea and malaise. It was probable that the legal difficulties attending the eree-

AND

SOUTH

WALES

BRANCH.

363

tion of high ventilators would shortly receive attention, as the municipal engineers were working in that direction. Flushing was, no doubt, very good, but any large increase in the volume of water poured down our sewers meant increased trouble on the limited area of our sewage farms, and water was becoming more and more precious every year. Dr. BOOBBYER gave a n a c c o u n t of s o m e cases illustrating t h e a~rial c o n v e c t i o n of small-pox, a n d was followed by Dr. PI~IESTLEY a n d Dr. MEREDITH RICHARDS.

PROCEEDINGS ENGLAND BRANCH SOCIETY HEALTH.

OF THE WEST OF AND SOUTH WALES OF THE INCORPORATED OF MEDICAL OFFICERS OF

AT the last m e e t i n g o f this b r a n c h t h e following p a p e r was read/: WHAT

IS A D A N G E R O U S

POTABLE WATER ?

By F. W. STODDART, PaNic Analyst to the City of Bristol. T h e q u e s t i o n of sewage p o l l u t e d d r i n k i n g water - - a l w a y s of great i m p o r t a n c e - - h a s lately a s s u m e d u n u s u a l p r o m i n e n c e for two r e a s o n s - - f i r s t t h e a d v e n t of cholera, s e c o n d l y t h e p u b l i c a t i o n of t h e r e p o r t of t h e R o y a l C o m m i s s i o n o n t h e Metrop o l i t a n W a t e r Supply. T h e f o r m e r r e m i n d s us i n t h e most forcible m ~ n n e r of the necessity for keeping a careful w a t c h u p o n t h e water we d r i n k ; t h e l a t t e r professes a m o n g s t o t h e r m a t t e r s to indicate t h e m a n n e r a n d d i r e c t i o n in w h i c h t h a t scrutiny m a ~ b e m o s t usefully d i r e c t e d . I p r o p o s e to confine m y r e m a r k s entirely to t h e form of p o l l u t i o n k n o w n as sewage c o n t a m i n a t i o n , a n d to a s s u m e m e r e l y t h a t t h e d r i n k i n g o f o r d i n a r y sewage is d a n g e r o u s in t h e sense t h a t specific infection m a y t h e r e b y b e conveyed. The question w h e t h e r or n o t d a n g e r is c o n f i n e d to o n e or two well-defined diseases I p r o p o s e to leave u n t o u c h e d ; t h o u g h this is, I v e n t u r e to think, a high!y import a n t m a t t e r w o r t h y of m o r e c o n s i d e r a t i o n t h a n it generally receives. F o r i n s t a n c e it has lately b e e n s h o w n t h a t c o n s t a n t l y i n h a l i n g sewer gases prod u c e d a d e r a n g e m e n t o f h e a l t h in a n i m a l s a n d r e n d e r e d t h e m very sensitive to t h e t y p h o i d baciIl u s ; is it n o t r e a s o n a b l e to suppose t h a t c o n s t a n t l y d r i n k i n g sewage e x t r a c t will h a v e a similar effect ? I n fact, I t h i n k t h e r e is direct e v i d e n c e t h a t drinking sewage n o t onl.y predisposes to specific disease, but even gives rise to definite disorders, n o t p e r h a p s at p r e s e n t r e c o g n i s e d as specific. N o w t h e a d m i x t u r e of sewage with water m a y a n d d o e s take place u n d e r two very different sets of c o n d i t i o n s ; i t m a y b e directly d i s c h a r g e d into a stream, well, or reservoir, or it m a y only r e a c h t h e l a t t e r after p e r c o l a t i o n t h r o u g h soil. T h e sewage as a w h o l e u n d e r g o e s very different c h a n g e s a c c o r d i n g as o n e or o t h e r of t h e s e condi-

364

PI~OCEEDINGS OF WEST OF ENGLAND

tions obtains, and it will be useful to look at them separately. It is chiefly the first class of polluted water, as exemplified in the Thames, that the Royal Commission had to investigate, and it will be conve. nient to consider the evidence laid before them and the conclusions they deduced before passing to the second class, as to which they had little to say. i . D i l u f i o n (Par. I 4 9 ) . - - N o w in the first case we have a simple dilution of the sewage with water presumably organically pure. How does this affect the question of infection ? I t is necessary to bear in mind that a typhoid or cholera stool is or may be a practically pure culture of specific organisms in a most active and vigorous condition, that on admixture with ordinary sewage such organisms multiply prodigiously, and that therefore the total sewage will, unless the physical conditions are too unfavourable, rapidly become strongly infected. Can we then state a definite degree of dilution beyond which the mixture of water and sewage becomes a safe beverage. T h e Royal Commissioners are apparently inclined to adopt this view, for they calculate that the maximum amount of infection possible under existing circumstances is in the Thames one case of typhoid to 294 million gallons, and in the Lea one case to x8o millions, and then proceed to suggest that this is a strong argument against the power of such water to convey infection. Is there any valid reason for this assumption ? Many of us know the storage reservoirs at Barrow Gurney, from which much of the water is supplied to Bristol. The maximum capacity of these reservoirs is 75o million gallons. Would it be considered reasonable to assume that the dejecta of two and a-half typhoid p a t i e n t s - - n o t single stools, r e m e m b e r - - m i g h t be discharged into this body of water without risk to the population of Bristol ? Besides, how is one to ensure the complete admixture of the dejecta with the water. Just as a few hundred gallons of water from the reservoir might be enormously polluted as they enter the main, so may the pollution of a river like the Thames be strictly local, inasmuch as there is a very large business and pleasure traffic upon it, apart from the towns which drain into it. What is to prevent the discharge of fcecal matter right over the intake of a water company ? Moreover, the supposition that the cases of typhoid are uniformly distributed throughout the year is a clear indication of the failure of the Commissioners to grasp the situation. Reference to any text book will show that about 5o per cent. of cases occur between August and November, when the proportion of cases will be increased from two to four times as compared with other months.

AND SOUTH WALES BRANCH.

A good deal is made of the fact that much of the sewage is treated by irrigation before passing into the river. It is at least worth consideration whether in such ease specific organisms have not a good opportunity of multiplying, and it is beyond dispute than in most, if not all, sewage farms much of the sewage escap.~s treatment altogether. 2. P e r s i s t e n c e (Par. iSo).---Then , in following the admittedly polluted water to its distribution, the Commissioners review certain considerations affecting the continuance of its infective powers ; and, first, as to the persistence of specific organisms : It must not be supposed (they say)that typhoid dejecta retain their infectiveness for an indefinite period. It appears to be the belief of bacteriologists that such dejecta begin to lose their viralence after a very few days, and the longest period for which the typhoid bacillus has as yet been found to retain its vitality when in fcecal matter does not exceed fifteen days. Now here, and indeed throughout this paragraph, there is a m'anifest confusion between prolonged vitality and maintenance of pathogenic virulence, two very distinct and not improbably inversely varying properties ; and it is more or less definitely assumed that if the bacilli have lost the power of giving rise to disease their presence may be ignored. Thus, the opening sentence reads : That such an occurrence, i.e., the carrying away of fcecal deposit by floods is possible, and, indeed, that it must occasionally happen is beyond question. There are, however, several important consideratioffs on the other side which must be taken into account before it is concluded that such an occurrence would constitute any appreciable danger. In the first place, the quantity of typhoid matter which could thus be washed down must be excessively small ~ and still smaller the amount of this which will still have retained its power of setting up disease. I should say that I can find nothing in the minutes of evidence to justify this confusion of two distinct factors; indeed, Professor Ray Lankester and Dr. Klein clearly suggest that virulence may materially alter whilst vitality is unimpaired, as has since been abundantly demonstrated with other organisms ; and I think to accept the views of the Commission on this point would be to close our eyes to a very serious danger. For if the infective power be lost, but the vitality r e t a i n e d - - t h a t is if the bacilli assume a merely saprophytic c h a r a c t e r - there is the obvious and real danger that by an inverse process they may re-acquire pathogenic powers, and may spread disease possibly at first in a mild and unsuspected form, returning by degrees to their initial virulence as a result of their return to a suitable habitat. Such a change of powers has long been known in the case for instance of the chromogenic bacteria, and I have observed something similar with the typhoid organism, T h e use of media containing antiseptics in the detection of this bacillus is well-known. Now I have found that with a medium of definite strength the success or non-success of an inoculation depends upon the age of the original culture. F o r

W H A T IS A D A N G E R O U S P O T A B L E W A T E R ? instance, a broth culture wilI remain capable of giving fresh cultures in ordinary broth ,for many months, but will not start a growth in the antiseptic medium if of greater age than about three weeks. If, however, it be first passed through ordinary broth, a culture in the antiseptic medium is obtained without difficulty. Here the bacillus soon loses some ot its powers, possibly including its virulence, but is readily restored fly a suitable environment. The danger of a succession of mild cases is obvious, and was indeed, I understand, a feature in the late small-pox epidemic in Bristol. Whilst admitting that this early loss of virulence is a reasonable supposition, the means at our disposal for determining the activity of the typhoid bacillus in this direction are by no means of the most satisfactory character, and do not approach in definiteness those employed in the case of other organisms such as anthrax. The question then resolves itself into one of continued vitality, and we naturally look for the authority for the very definite limit of r 5 days already quoted. The reference numbers in the margin of the report are those attached to two of Dr. Sims Woodhead's replies which form part of his examination as to the duration of vitality of the typhoid bacillus in water, sewage, and fceces. It would b e impossible to represent the tenor of this evidence by quoting one or two replies, a~:d as the whole of this very important part of the report is based upon this evidence, I shall ask you to allow me to read it verbatim. Dr. Ogle is examining, and asks : - ~3,o96. Can you tell me how long the typhoid bacillus has b~en known to live in water ?--It has been said to live for about 15 days, and even longer. I3,o97. In ordinary water ?--In ordinary water. x3,o98. In river,water ?--Yes. I3,o99. It has been said to live z5 days in ordinary river water ?--About I5 days, yes. I3,mo. I think in distilled water it has lived longer?~ In distilled water it has lived longer. I3,IoI. But the question of distilled water does not touch us ?--No. x3,ro2. But in river water it has lived for a fortnight or I5 days ?--Ye~. One does not carry all these things exactly i,.~one's head. There have been a number of experiments on which I do not place the slightest reliance, in which it has been said that it lived longer. z3,m3. But in the best experiments, those in which yon should put yourself the most confidence, r 5 days or thereabouts has been the extreme limit of its maintaining its life ? --~xreS.

I3,Io4. And in water which is diluted with sewage it is even a shorter time ?--A shorter time. r3,IOh. And in Ieeealmatter itself?--Probably shorter still. I3,IO6. Is it possible to lay down any period during which it woMd live if it was left in a mass of fceees ?--I do not think it is at present. 13, Io7. But it is a very short time ?--Probably a short time. I3,1o8. A time that would be measured probably by days you mean, I suppose ? Yes. I n the succeeding replies Dr. Woodhead goes on to say that his faith in the limit of fifteen days is shaken by his own observations in a case of typhoid-infected sewage.

365

I am unable to find the original authority for this limit of fifteen days, but Dr. Woodhead probably had in his mind the following passage from his most ,valuable little work "Bacteria and their Products" (p. x98 ). It is a somewhat important fact that the typhoid bacilli may-remain active for a considerable length of time in the stools, for the bacilli in fceces kept in a sterilised tube for 15 days remain alive at the end of that period, and vigorous cultivationscould be made from such material. How far this supports the finding of the Commission I leave you to judge. Now the fact is that although this bacillus may be recognised with tolerable certainty in pure cultures, and in waters containing only the usual water bacteria, there is at the present moment no method in existence which will enable one to detect it with anything like certainty in the presence of numerous organisms constantly occurring in sewage. Hence the statement that it has not been detected after so many days/has only a negative value. The following observation also suggests a possible source of error in the same direction. On February r3th, I894, 500 c.c. of good tap water, in which no organism can be confused with typhoid occurs, were placed in each of two sterilised bottles, A and B, and after sterilising at i oo ° C , both received i drop (I/3o c.c.) of a broth culture o f typhoid. Cultures were made from these at intervals, but towards the end of June it was noticed that growths were not obtained with certainty without vigorous shaking, and that this was especially the case with B. On July r2th cultures could still be obtained from A, but none of any kind from B after repeated and violent agitation. The water was then poured out of B, and a few c.c. of sterilised broth introduced, when an abundant development occurred of various forms, amongst which typhoid was readily detected. Now, the only reasonable explanation appears to be that settlement of the organisms had taken place with the formation of a tenacious film, such as forms in a filter ; and that the resistance of this film to shaking was increased by the presence of the water bacteria, so that finally it was impossible, with the utmost amount of agitation admissible in a plug-stoppered vessel, to detach organisms whicb, however, were very ready to develop in a suitable medium. It is evident that no experiment on the persistence of vitality of any organism is conclusive which does not embrace the examination of the vessel as well as of the contained liquid, and that otherwise there is a danger of assuming the death of the organisms prematurely. Moreover, it is obvious that if the organisms had deposited on the muddy bottom of a stream, they would be liable to be carried off by a flood in an active condition. I n sterile waters and in sewage free waters the typhoid bacillus can certainly be detected several (five) months after inoculation, and may even

366

P R O C E E D I N G S OF W E S T O F E N G L A N D A N D SOUT[-I W A L E S B R A N C H .

multiply in the meantime; and until we are in possession of a test that will enable us to positively ascertain its absence it will certainly be unsafe to accept fifteen days as the limit of vitality; and even if it be admitted that the pathogenic virulence is impaired, it does not follow that " i t is only typhoid dejecta of very recent deposit from which danger is to be apprehended." Indeed, I suspect that a considerable body of evidence to the contrary could be gathered from a perusal of published reports upon outbreaks of enteric fever not arising from recent cases.

3. AntagoMsm (pp. 152 and x 5 3 ) . - - T h e question of persistence is very closely connected with that of antagonism between organisms in the same medium, as to which the report states, and states correctly, that : It appears to be the generallyaccepted docfrlneof bacteriologists that the pathogenic organisms and the ordinary river bacteria to which the decompositionof organic matter is due are naturally antagonistic, and that these latter undoubtedly exert an influencein diminishingthe vitality of the typhoid bacillus. Now the evidence upon which this widelyaccepted doctrine is based is really the weakest kind of negative evidence, whatever positive evidence has been adduced being in flat contra. diction to it. The arguments in favour of this view are, I think, chiefly these : - (a) Antagonism has been proved to exist between certain micro-organisms, e.g., prodigiosus and cholera, anthrax and Fried]//nder's pneumococcus, etc. (3) Experimenters mostly agree that the bacilli of typhoid can be found at a much later date in sterilised water and sewage than in unsterilised. On the other hand direct experiments have been made with the commonest water o r g a n i s m - - t h e bacillus fluorescens--and it has been distinctlyshgwn that it has no prejudicial action upon typhoid (Ray Lankester) or anthrax (Marshall Ward). And it is becoming more apparent every day that special methods must be devised for separating each species in mixed cultures. This has been done more or less completely with cholera, but even there Gruber has shown that cholera may be temporarily overwhelmed by putrefactive organisms, and yet may be detectable months later when the latter have died out. Dr. Percy Frankland has shown of so well marked a species as anthrax that a culture may be so modified as not to give rise to growth when inoculated into broth, nor even to cause anthrax symptoms in an animal, and yet may b~ revived by the direct addition of nutritive matter so as to give both results. No such successful method has been invented for typhoid, that recommended by Parietti and in best repute just now, not only failing to isolate the bacillus, but actually suppressing it when present.

I have been for the last two years in search of such a method, and have now some hopes of success. Lastly, sufficient attention has not always been paid to chemical alterations brought about by the process of sterilisation. We shall see that light is practically inoperative except in the presence of abundance of oxygen. Sterlisation by heat~ of course, goes far to remove this gas, and it is possible that filtration under diminished pressure may act in the same direction ; hence experiments not carried out in complete darkness may be invalidated in this way. Considerations of this kind should make us very cautious in accepting unreservedly any of the definite statements that have been made on the limits of vitality of the typhoid bacillus in the presence of other organisms. 4. Actio~ ofZighl (p. t 5 3 ) . - - W e next turn to the action of light on micro-organisms referred to in the next paragraph of the report in the following t e r m s : - In the case of these deep welts there is moreover anothe~ condition, wanting in the rivers, that is favourable to the development of the pathogeniabacteria being one of the con. ditions under which they grow in their natural habitat in the alimentarycanal, namely darkness. For it is found that while exposure to direct sunlight destroys these bacteria, even such a tempered amount of light as is present under ordinary conditions in Thames water injuriouslyaffects their vitality. Now this is certainly going further than the evidence justifies. This paragraph is based upon Dr. Sims Woodhead's replies Nos. 13,12 i-3, which are as follows : - 13,I21. What are the conditions that would interfere with their maintaining their vitality ? One of the conditions is the action of light in clear water ; of course not acting nearly so well in muddy water, or at some little distance away from the surface. I3,I22. YOU mean in such water as the Thames water would be. You call that clear water do you not ? Comparatively clear water. I3,I23. The ordinary condition of the Thames and the ordinary condition of the light would be suchas to affect the vitality of the bacillus? Certainly to some extent, in the superficial layers of water. T h e n the Commissioners proceed to quote the preliminary statement by Dr. Woodhead, " that ia the laboratory we are compelled to keep all our pure cultures which are under favourable conditions of growth, in a dark cupboard ; otherwise they would die out, rapidly becoming weaker and weaker. The same, of course, must be the case where as in water under the open air organisms are exposed to l i g h t " ; but actually omit the latter half of the last sentence, which reads " t h o u g h the power that water, even apparently clear water, has of cutting off a large proportion of the active light must here be carefully borne in mind in considering this question." Moreover, no mention is made of the absolute necessity of an abundance of oxygen in this mode of sterilisation. Whilst this action of light and oxygen had been thoroughly investigated as long ago as I877 by

WHAT

IS A

DANGEROUS

Messrs. Downes and Blunt, at the time of the report there had b e e n no exact experiments bearing upon the effect of interposing a layer of w a t e r ; and as s o m e later researches are extremely contradictory I have attempted during the past six months to arrive at s o m e definite conclusion, and though m u c h interrupted by unfavourable weather have obtained some results of interest. T h e problem is to find in what way the action of light is modified by the interposition of a layer of water of varying character and depth, and it is not sufficient therefore to diffuse the organisms through the water, but it is necessary to define their exact distance from the surface. T h r e e waters were employed in these experiments ; a bright, practically colourtess water ; m u d d y water from the Avon, the opacity of which

WATEIR

DEPTH OF,.

,

__o

--

_

POTABLE

~

I

o

367

affected in a week by t h e light in the least, all giving an a b u n d a n t growth of typhoid. As the week in question was a bright one, with plenty of sunshine, the only likely explanation of this/allure was want of oxygen. I n order, therefore, to correct this deficiencT, and at the same t i m e to form a m o r e correct idea of the progress ofsterilisation, I finally a d o p t e d the following course, T u b e s of about i ~ inch diameter were charged with the least possible quantity ofagar-gelatine m e d i u m , steritised by heat, inoculated with typhoid, and sealed with the blow. pipe. T h e y were then placed obliquely in the tanks, so that the portion covered with m e d i u m was uppermost, and at a depth from the surface of the water varying from 2 5 m.m. to ~2 5. m,m. ( I ~ 5 inches). T h e three series were started at EXPOSURE

P

WATER?

IN

P ,, M

o

DAYS.

"'-~

.~

M

II ml I'

, q 0 ~

l L I G H T STERILISATION IN WATER. c, clear; P, peaty; r,~, muddy.

was such that a piece of white paper was invisible at a depth of three inches ; and a peat-stained water previously filtered and quite bright. M y first experiments were m a d e with flatb o t t o m e d flasks, such as I am a c c u s t o m e d to use for plate cultivations, but owing to the difficult7 of securing the necks of the flasks I was only partially successful, though I found that flasks at a depth not exceeding two inches in the A v o n water were sterilised in a fortnight. I then enclosed broth in flat glass tubes, which were inoculated with typhoid and sealed before the blow.pipe. Ot these tubes some were placed in water at depths varying from half an inch to six inches, others were kept in the dark, and others exposed in a south window. N o n e of these were

ten a.m. on J u n e 2oth, and tubes were r e m o v e d daily at the same hour. Seven unexposed tubes developed normally : TABLE SI=IOWINGDEPTH TO WHICH STERILISATION IS EFFEC:rED m DIFFEaENT WA'r~Rs. Exposure Days.

I z 3 4 5 6 7

...... ..... , ...... ...... ...... ...... ......

Depth of Water (m[llimetres). Clear :Peat Muddy Water. Water. Water.

Light Iq.ecord.

3,726 7,355 4, °66 4, 69o 4, 540 3,55 ° 4,056

...... ...... .

.

.

.

.

I25 ...... ,. . . . . . . .

.

.

...... ,, ....... , ........ ...... ,,

• . . . . .

...... ...... •..... . .....

25 30 30 45 ~ 30 -40

...... ...... ...... ...... ...... ...... ......

3° 3° 35 ---5°

This tube became detached, and floating too near the surface was apparently sterilised to a greater depth than was actually the case.

368

P R O C E E D I N G S OF W E S T O F E N G L A N D AND S O U T H W A L E S B R A N C H .

The table shown summarises the results, the value of which is greatly enhanced by the addition of a record of the actinic power of the light day by day. These data were most kindly furnished me b~' Dr. Richardson and Mr. Quick, of University College, by whose chlorine actinometer they were obtained. This instrument is described in the i~M/oso~Mcal Magazine, i 8 9 i , p. 277. I am further much indebted to Dr. Richardson for many valuable suggestions. It will be seen that complete sterilisation took place in air and in clear water within twenty-four hours, but that no sterilisation took place in the other waters at a greater depth than So m.m. (2 inches) even at the end of a week. It now became desirable to repeat the experiment with clear water to ascertain how rapidly sterilisation proceeds, and if clear water retards at all. Tubes similar to the above, therefore, were placed horizontally at the bottom of a tank and covered with 25o m.m. (io inches) of bright water, another series being placed in air. Exposure took place on July 1st, tubes being removed hourly from Io a.m. to 6 p.m., all the tubes being in brilliant sunshine all the time. The results were as follows : Light Record. Air. Water. IO--II ... 629"5 ... Growth ... Growth. Io--I2 ... 648"3 ... Sterile ... Slight growth in thickest part. Io-- x ... 686"r ... Sterile ... Sterile. All subsequent tubes sterile. Four additional tubes kept in the dark developed normally. Having now ascertained the range of action of sunlight for these waters I returned to the flasks which give more striking pictures, and emphasised any effect by Buchner's method of painting an opaque design upon the exposed surface. These cultures, which were exposed from ten a.m. to six p.m. on a bright day at a depth of 5 o m m . (2 inches) from the surface, I now produce, and it will be seen that no sterilisation took place in the case of the peaty and muddy waters, but that the cukure was entirely sterilised in clear water, except where protected from the light. To complete this part of the research experiments were then carried out in a fairly clear natural water, representing more nearly a river water such as might be used for a water supply. This water completely obscures a piece of white paper at a depth of 2 feet 6 inches. Flat-bottomed flasks were sunk in this water at depths ranging from one to four feet, and exposed for a week : the first flask was plainly visible at a depth of ~ foot ~ none of the others could be seen. The light record for this week was 36,462 units, and the temperature of the water on the last day 17'4 ° C. On examination it was found that normal development had taken place in all the flasks except that nearest the surface, and in this no growth resulted on incubation.

I gather from these experiments that sterilisation by light in presence of abundant oxygen fails in a simply turbid water at a point somewhat nearer the surface than that at which a white paper ceases to be visible. For instance, on June 17th the water of the Severn at the intake of the pumping station (then in action) of a certain important town was such that a piece of white paper was invisible at a depth of 23 inches. Any pathogenic organisms at the orifice, which is considerably deeper than this, would be unaffected by light. The medical officer of this town, in his annual report for I893, says : - I regret to have to announce that since the Severn water has had to be used, a large increase has taken place in the number of typhoid fever cases notified in this City. I do not pretend to say positively that the Severn water is the cause, but I can find no other explanation for it, and I am informed that this disease is prevalent in towns further up the river, and which drain their sewage into it. It will be noticed that in all these later experiments by far the greater portion of the ~essels used was filled with air. Now this is a point of the utmost importance, and I am endeavouring to ascertain the minimum of oxygen necessary to effect sterilisation. I have found that a tube two-thirds full of broth and stopped with a cotton plug can be exposed for a whole day to bright sunshine without any evidence of sterilisation. Now the saturation quantity of oxygen for water at the ordinary temperature is about 2 cubic inches per gallon, or '75 per cent. by volume, corresponding to 3'75 or, say, 4 per cent. of air. If, then, 33 per cent. of air is insufficient, it appears that in a river the great bulk of water can never be sterilised at all. Of course, I am aware that this portion of the argument is at present very ,ncomplete, but as far as my investigation has gone, and especially bearing in mind that organisms are destroyed by light with more difficulty in water than in culture media, I think I am justified in saying that in natural waters sterilisation by light is so imperfect that it should not be relied upon as a protection against infection. It should be borne in mind that all these results were obtained in exceptionally brilliant weather, and that the cultures were fully exposed to the sun during the whole time. 5. Seltlcment (p. i53).--Settlement of bacteria whether alone or with particles of suspended matter has an important temporary effect, but i n referring t o the experimental evidence on this head the Commissioners forget to add to the statement that 98 per cent. of the contained organisms settled down with mud, the further statement that the organisms may be re-distributed throughout the water within 24 hours, and that Dr. Percy Frankland, by whom this part of our subject has been chiefly investigated, expressly states that this form of purification is not

WHAT

IS A

DANGEROUS

to be relied upon. Indeed, it is open to doubt whether the removal of bacteria from the influence of light and air, and their storage in a position from which they will be removed by every flood is any advantage. 6. Dase a f Organisms (p. I 5 8 ) . - - I need only briefly refer to the paragraph in which the dose of bacilli necessary to set up disease is discussed. In the present state of our knowledge any proposal to establish a numerical maximum of pathogenic organisms which may be permitted in a potable water will not, I am sure, meet with the approval of this meeting. Besides there is nothing in the evidence to support this. On the contrgry, all the witnesses disclaimed any knowledge of the quantity of typhoid bacilli necessary to set up disease. It would appear then that there are no sufficient grounds for assuming that the raw water of any stream into which sewage is discharged is a safe supply for drinking purposes ; is the position improved by filtration ? 7. fi'zTtration (p. t54-6 ). - - N o w it has been placed beyond doubt that simple sand filtration in its most perfect form will remove a very remarkably large proportion, often exceeding 99 per cent., of the micro-organisms of all kinds present in water, and this has naturally been advanced as a proof of the safeguard afforded by this process. It must not be forgotten, however, that the small residual fraction represents no inconsiderable number of organisms. Dr. Percy Frankland puts the average number of residual organisms in the filtered Thames water from the mains at 4o0 per c.c., or four times the maximum suggested as admissible in a filtered supply; and though this number is probably greater than exists in the water immediately after leaving the filter, it detracts to my mind considerably from the sense of security afforded by a contemplation of the percentage re. duction. A more serious consideration, however, is the certainty of occasional failure where such immense filtering areas are employed. The well-known breakdown of the Altona beds, and the consequent outbreak of cholera, proves the reality of this danger. If this could occur during the comparatively short epidemic, is it not likely that it would occur pretty frequently in ordinary practice ? Indeed, an inspection of Dr. Frankland's monthly reports shows pretty plainly that this does occur, and that the variation in the number of organisms passing the filter's of the London companies is very considerable. Thus in November and December, i886, we find the following figures : - Thames

. . . . . . . . .

Chelsea •. . . . . West Middlesex . . . . . . Soathwark

......

Grand Junction . . . . . . Lambeth . . . . . . . . .

~tffovember. 56,coo

.........

65 ......... 47 ......... 321

..........

8o ......... IO8 .........

December. 63,ooo

2z2

2,ooo I , IOO

x, 7oo 305

POTABLE

WATER?

369

Here, although the initial proportion of organisms is not very different, the number pas~ing the fitters is from three to forty times as great in December as in November. This was n o t improbably the effect of frost ; but the fact that 3 per cent. of the organisms can penetrate through the filter is quite a serious matter ; in short, a too implicit reliance on this mode of purification may well be a source of danger in the future, as it certainly has been on more than one occasion in the past. Dr. Klein, after pointing out that no kind of filter, not even excepting the porcelain cylinder, is continuously germ proof, sums up the matter in these words: " N o filtration is reliable to do away with all risks," and repeatedly emphasises this point in his replies (ro,942-5, io,953 , Io,983, etc.) 8. Analysis (p. ~4~).--What in the next place are the means available for detecting this form of pollution ? There are two main methods of ascertaining the admixture of sewage with natural waters, the chemical or biological examination of samples, and local inspection. Under the circumstances we are now considering chemical examination is placed at a great disadvantage, as will be seen on looking at the quantitative effect of dilution on the characteristic constituents of sewage. Take albuminoid ammonia for instance--a grain per gallon would be a very full average. Dilution of the sewage with about 25o times its bulk of pure water would reduce the albuminoid ammonia beyond significance. Other constituents such as chlorine, which may be put at to grains, would even more rapidly lose their value as sewage indications. Except then in the shape of series of analyses along the course of a stream, useful information is not often obtainable by the chemical analysis of the water of rivers, especially if of large size, though of course results pointing to contamination, if such are obtained, are aU the more significant. The Commissioners, however, take another view of water analysis of an altogether extraordinary kind. They appear to regard the quantitative estimations comprised under the name of water analysis as being intended to determine the quantity of organic matter present, and then argue that the days of water analysis are departed, because this organic matter may be harmless, and refer to the substitution of a "better test," a Fparenfly of a biological kind. It will scarcely be necessary to point out that all this is entirely erroneous, the sole object of the quantitative estimations being to ascertain the quality and source of the polluting matter, quantity being a very secondary consideration. The biological tests are at the present time scarcely as decisive in results as the chemical, though I hope shortly to show that useful information may be obtained by a modified method. Local inspection then remains the most useful

37 °

PROCEEDINGS

OF W E S T OF E N G L A N D A N D S O U T H W A L E S BtLANCH.

proceeding with this class of water, for in the great majority of cases direct pollution with sewage must be capable of demonstration. Having then dismissed chemical evidence as out of date, and biological tests as still in their infancy ; having, in short, characterised the one as senile and the other as puerile, the Commissioners turn with evident relief ~;o the teaching of experience, and this they take under two heads, the effect of the present supply on the health of London, and general evidence as to the conveyance Qf disease by river water. On the first question the Commissioners come, as on the evidence they were bound to come, to the conclusion that in no single instance has the consumption of this water been proved to cause disease ; and as the conditions have remained practically unchanged for thirty years this is no doubt a very strong piece of negative evidence. On the other hand, two very experienced observers, Drs. Frankland (4,575) and Woodhead (z 3,080) flatly decline to endorse the conclusion that typhoid is not and cannot he disseminated by the use of this water, and the latter states (,3,o9~) that he would not drink any London water without first treating it by a process which would ensure sterilisation. On the second head the Commissioners declare themselves unable to accept the conclusions of Dr. Barry as to the Tees Valley epidemics, the only instance of alleged conveyance of disease by river water of which they take notice ; and they were evidently influenced in this by the consideration of dilution, a point already dealt with. It is curious that just about this time a dearly demonstrated case of river-borne typhoid occurred at Lawrence, in the United States, and another at Chester-le-Street, in Durham, the water having been filtered in both cases. Two other instances were brought before the Commission, one by Dr. Turner (4,725) relating to the Lea, and another by Dr. Seaton, who proved completely to his satisfaction that typhoid was conveyed from Godalming down the River Wey for upwards of a mile. Both were apparently ignored by the Commissioners, who make no mention of them in the report. Let us then pass to the second form of poIIution~ namely, that where the sewage is not directly discharged into the water, but slowly percolates through the interstices of the soil, only gradually mixing with the subsoiI water. Here there exists an entirely different state of things. We shall have the centre of pollution--say, a cesspit--situated within an area of more or less elliptical shape, its long axis in the direction of natural drainage, and elongated in proportion to the rate of flow. Over this area we shall get a mixture of sewage and water in proportions varying with the distance from the source of pollution.

With reference to the ground already covered, I need only say that the absence of light, .the comparatively uniform temperature, and the gradual dilution are all probably favourabte to the persistence of pathogenic forms. But the special features of the case under notice need some attention. And of these the most important is the question of natural filtration. It is often tacitly assumed that the subsoil is a thoroughly effective filter, and that evidence of percolation sufficient to remove the grosser matters is evidence of satisfactory purification. I n taking this view it is overlooked that there is little or nothing in common between the action of the sand filter and that of the subsoil in effecting the purification of water. The sand filter in its most perfect form produces no chemical improvement in the water, but solely by mechanicaI action removes suspended matter, including microbes. Its efficiency therefore depends upon the perfection of the mechanical arrangements, of which the most important are the following : (i) A certain fineness of material; (2) sufficient depth; (3) uniformity of Imrticles of filtering medium; (4) regulated rate of flow; (5) protection against accidental disturbance; (6) renewal of material when necessary. Now the subsoil does not comply with any one of these conditions ; indeed, water does not commonly pass through material of which if is composed unless this is gravel or sand, but along the partings and fissures ; and whatever path it takes it naturally enlarges day by day by solution or disintegration, or both, so that to get the s~me amount of surface contact an enormously greater thickness of filter bed is required. The rate of flow, so far from being adjusted to the filter, is at the mercy of numberless accidents quite beyond c o n t r o l . But the very circumstances which prevent the subsoil from being an efficient mechanical filter add to its power of dealing biologically with the unorganised matter of sewage ; for the opening up of the subsoil furthers its a~ration, and so supplies one of the essential conditions for the vigorous action of the nitrifying organisms. But the fact that the chemical constituents of sewage are so broken down by microbic action that the originally offensive compounds are resolved into inoffensive salts is no kind of guarantee that living pathogenic organisms are removed ; indeed, many of these latter actually take part in this very process, and I found last year in connection with this subject that the cholera spirillum was apparently unaffected by the presence of these useful organisms. There being, then, no necessary parallelism between the series of processes known as nitrification, and the elimination of pathogenic organisms, it is impossible to fix upon any stage of the former as that at which danger ceases. It is quite possible that the danger of infection

P R O C E E D I N G S OF

THE

may survive the chemical evidence of pollution, and I think decidedly that the only safe course is to discard water in which there is clear chemical evidence of the presence of sewage products. I have shown elsewhere that nitrification is often completed within three yards of the source of pollution, but that at a distance of ~oo feet and upwards the chemical evidence of pollution begins to lose its force, though, of course, these measurements may vary considerably according to circumstances. This brings us to the means of detecting this form of pollution. Thanks to the fixation of practically all the nitrogen of the sewage, and the delicate tests we possess for the nitrogen acids, we are able to be much more precise in detecting sewage in this shape ; here, indeed, chemical evidence is not only useful but indispensable. For inspection is in many cases worse than useless, it is misleading. Of this I could give numerous instances, but will content myself with reminding you of the frequency with which remnants of old and forgotten drainage systems, often not entirely disconnected from more recent work, are found to be sources of pollution. For arriving at the sanitary value of a well water, I repeat chemical analysis is by far the best guide, and though infection may theoretically be conveyed by an apparently pure water, I do not think this often happens ; on the other hand, as the chemical indications disappear at about the distance experience has shown to imply sufficient natural filtration to afford a reasonable protection against infection, there is little likelihood of doing an injustice to wholesome water. The reply, then, to the title of my paper should be somewhat as follows: A dangerous potable water is one into which sewage is known to be discharged, or which is shown by chemical analysis to contain sewage prodacts ; and though filtration, if perfectly carried out, is a considerable safeguard, it is no absolute protection, and is only to be considered a makeshift to be employed where unsatisfactory water must be used. ~ S T R A N G L E S " A N D DIPHTHERIA.--In the case of two young men, at Minsterworth, who were notified as suffering from diphtheria, I ascertained that the one who first developed the disease had been taking care of a horse which had suffered from the "strangles," a form of affection which appears to be distinctly diphtheritic in type. He communicated the infection to his brother, who slept with him. Fortunately the equine and human patients all recovered. This is the only occasion in which I have had any reason to attribute the infection of diphtheria to one of the lower animals, though cases of derival from cats are on record.--Annual Repo~t, 1893 , of Zgr, F. 2"..Bond, Gloucesters~ire

Combined Distrtct.

NORTHERN

BRANCH.

371

P R O C E E D I N G S OF THE NORTHERN B R A N C H OF T H E INCORPORATED SOCIETY OF M E D I C A L OFFICERS OF HEALTH. A MEETINGof this branch was held in the Mayor's Chamber, Town Halt, Durhams on June 29th. Present: Dr. H. E. Armstrong, president, in the chair ; Drs. Hall, Turnbutl, Wood, Hembrougb, Jepson, Vann, Park, Stokoc, Gofton, Lam'ence, Eustace Hill, and G. R. Murray. The PRESIDENTannounced the death of Dr. T. Gibbon, of Seaham Harbour, a member of the Branch, and it was resolved that a vote of condolence be conveyed to Mrs. Gibbon in her bereavement. Letters regretting inability to attend were read from Drs. F. W. Gibbon, Hepburn, and Walker. A letter was read from the Secretary of the Sanitary Institute announcing that the annual congress of that Institute would be held in Liverpool on September 24th and following days, and asking the Branch to appoint two delegates. It was resolved that the Vice-President (Dr. Hall ) and the Hon. Secretary do attend the congress as representatives of the branch. On the invitation of Dr. Goffon, it was resolved that the next meeting of the branch should be held at Tynemouth at the beginning of October. The HoN. SECRETARY reported that the President and himself had attended the meeting of the sub-committee composed of representatives of the Society and the branches, which was held in London in May, and announced the recommendations of the committee with regard to the various matters considered by them. The HON. SECRETARYstated that he had received a letter from Dr. Mitchell, of Hebburn, who regretted that owing to serious illness he had been unable to prepare his paper on the " Relation of Ashpits to the incidence of Typhoid Fever." The following gentlemen were elected members of the branch: J. Hague Clegg, M.R.C.S., M.O.H., Stockton; W. Dalziei, L.R,C.P., late M.O.H., South Shields; J. w. Hembrough, M.D., L.S.Sc,, M.O.H., Northumberland C.C. ; T. Livingstone, M.D., J,P., M.O.H., Weardale R.S.D. Dr. AR~aSTRONO introduced the question of granting certificates under the Customs and Inland Revenue Act respecting the sanitary fitness of houses, and stated that his action in declining to give a certificate had been complained of to the Town Council of Newcastle by the Newcastle Industrial Dwellings Company. The Council had referred the matter to the Sanitary Committee for report. A similar complaint had been made to his Sanitary Committee by a deputation from the Newcastle-upon.Tyne and District Property Owners' Association, headed by their chairman, who was also a member of the Sanitary Committee.