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Incorporated society of medical officers of health
NEWCASTLE
CHOLERA
rain has been recognised by the New York Health Department, who have issued a circular ~ to medical men there explaining the arrangements made for this purpose. They say : " The differential diagnosis between true and false diphtheria can be made by bacteriological examinations within twelve hours, while without their assistance it is difficult or impossible. The Health Department is now prepared to make use of bacterial cultures in all cases of suspected diphtheria." The circular then proceeds to say that the medical man in charge may obtain the necessary culture tube free of cost from various centres, to which he will return it after inoculating it from the suspected throat, and the tubes will be daily sent on to the department from the local centre, or an officer of the board on receiving a request will attend and make the inoculation. By noon on the following day the medical man receives the result of the culture by telephone or through the post. There is no reason why this example should not be followed in this country. The expense of carrying it out would be trifling compared with the outlay entailed when a throat affection is true diphtheria, or is supposed to be so. I n London the Metropolitan Asylums Board would be the proper authority to take this matter up, and arrangements might be made with some central bacteriological laboratory to provide the culture tubes and make the cultivations. A supply of tubes might be kept at the of~ces of the boards and vestries, and each medical officer of health would deliver them to medical men applying, and would receive the report of the bacteriologist next day and convey it to the medical man in charge. But I would go further than this, and require that no case should be allowed to be removed from isolation, either in hospital or at home, until it had been proved that the throat were free of the bacillus, because it has been shown that virulent diohtheria bacilli may be found for an indefinite time after the apparent cure of the malady, and infection may be spread thereby. Especially in cases treated at home, I am inclined to the opinion that the patients are allowed to mix with healthy person at too early a stage, but, without the definite evidence given by finding the bacilli still there, it would be difficult for a medical man to insist on further isolation when the patient was to outward view apparently well. If diphtheria is to be stamped out, I feel sure that greater insistance must be laid on this point before disinfection of premises and clothing are caxried out. CONFERENCE ON SMALL-POX AND VAGRANTS,T h e Public Health Committee of the London County
Council have decided to convene a conference of urban sanitary authorities, to be held during July at Spring Gardens, to consider whether any measures can be taken to restrict vagrants as agents in the spread of small-pox and other infectious diseases. * "Journal of Laryngol0gy," October, I893.
STERILIZER.
339
INCORPORATED SOCIETY OF MEDICAL OFFICERS OF HEALTH. 2II"eetingof Memb.'rs, May zlst, x894. NEWCASTLE CHOLERA
STERILIZER.
DR. HENRY E. ARMSTRONG exhibited a model of the sterilizers provided by the sanitary authority of Newcastle.upon.Tyne for the hospital which they erected last year in anticipation of an outbreak of cholera, and said the Society had some time ago brought before them by Dr. Sisley a description, with drawings, of the cholera excreta sterilizer at the Alexander Hospital, St. Petersburg. That apparatus, though excellent in principal and original in design, was too elaborate and too costly for general use. It consisted essentially of a lareg central receiver, to which the excreta were conveyed by pipes from the different wards for subsequent sterilization in a steam jacketed boiler. These pipes--which in a large hospital would be of very considerable length:--together with their inlets, would be continually lined by a layer of infected excreta. There were also electric and other complicated appliances connected with the sterilizer which would be liable to get out of order. These objections were obviated in the cholera sterilizer, of which the exhibit is a model. Five of the sterilizers had been made for the Newcastle Cholera Hospital erected last summer. They were manufactured by Messrs. Goddard, Massey, and Warner, Nottingham, on the design of Mr. Wm. Warner, of that firm, acting under the instruction of the City Engineer of Newcastle-upon-Tyne, Mr. W. George Laws, M lnst,C.E, and the Medical Officer of Health. The apparatus, of which an illustration is given, consists of a ~o-gallon cast-iron sterilizing vessel, having in its top side a circular opening nine inches in diameter, with a hinged and balanced lid capable of being closed and made steam-tight. Communicating with the interior of the vessel are four pipes, viz., (i) a steam supply pipe, terminating near the bottom of the vessel, for sterilizing; (2) a steam eject pipe, terminating in the upper part of the vessel; (3) a water pipe for washing o u t ; and (4-) a pipe four inches in diameter for the discharge under steam pressure of the contents of the vessel after disinfection. The sterilizer is not jacketed. Its capacity is based on the estimated requirements of a ward of twenty beds. It is placed in an offshoot of the ward, corresponding to the chamber of a water closet. Into it are emptied tide evacuations, floor washings, and slops of all kinds. The exhibitor had had the idea of having the circular opening sufficiently large to admit a bed pan, but this was thought by Mr. Laws to be likely to weaken the apparatus, and was not attempted. The inlet is arranged to serve as the seat of a closet for convalesce~ts, and a wooden rim is provided for l~ying over it before such use. Z 2
34 °
D I S I N F E C T I N G H U L K OF R I V E R TYNE PORT SANITARY A U T H O R I T Y .
The modus aperandi is as tollows : Whenever the sterilizer is sufficiently full to be ready for disinfection, which may be once or twice every hour, an attendant is summoned, and enters the closet by an external door. He then fixes down the lid by means of the screws, and turns on steam for disinfection. In about seven minutes the pressure rises to 30 Ibs. After ten minutes more he opens the cock of the steam ejector, and closes that of the steam pipe for disintecting. He next opens the discharge valve, and the contents of the sterilizer are ejected into the tank, there to cool before being sent into the sewer. The cost of the sterilizers, apart from the steam appliances, is .~3o each. DISINFECrING [~IULK OF THE R I V E R T Y N E PORT
SANITARY AUTHORITY, The difficulty recently experienced in dealing with ships arriving from infected ports, and especially those infected with cholera, has created a need for more complete means of disinfection of vessels and their contents throughout than has hitherto been employed. During the cholera prevalence of the past two autumns the River Tyne Port Sanitary Authority, whilst fully appreciating the importance of the thorough disinfection of infected ships and their contents, has realized the inefficiency of the ordinary means and appliances. The Holt system, named after its organizer and developer, and cmTied out by him at New Orleans, has probably been hitherto the best in the world. The disinfection by steam and perchloride of mercury, in that system, is excellent. But the wholesale burning of sulphur, which is the third part of the system, is attended with risk of fire, and is otherwise open to objection. Apart from the mere difficulty of finding an available site for a disinfecting station on the shore of a port, the propriety of having such a fixed station in m o s t English ports is, to say the least, doubtful. In comparatively narrow river ports the danger to the floating and riparian populations of permitting an infected or suspected ship to pass upwards is sufficiently obvious. Besides, the free use of perchloride of mercury for disinfecting ballast and bilgewater in the upper reaches of such ports will poison the fish, a special objection in salmon streams Iike the Tyne. The use of liquefied sulphurous acid instead of burning sulphur does away with danger from fire. The objections to a disinfecting station fixed on land are obviated by the provision of a floating one to go to the infected ships instead of having them brought to it. The excellence of this suggestion, for which we are indebted to Mr. W. George Laws, C.E., was at once recognised by the writer and recommended to the Port Sanitary Authority, who approved and adopted the proposal. Messrs. Goddard, Massey, and Warner were invited to
prepare plans and estimates for a complete set of disinfecting apparatus in accordance with the report of the Medical Officer of Health, and the proposals of Mr. Laws, including (i) a steam disinfector for clothing, bedding, rags, etc. ; (2) apparatus for effectually douching decks, floors, woodwork, sand ballast, certain cargoes, etc., with a i-5oo solution of perchloride of mercury ; and (3) a plentiful store of liquefied sulphurous acid for fumigating berths, crew spaces, 'tween decks, or other infected places on shipboard. The plans were adopted, the machinery was ordered, a hulk was purchased to hold it, and on the request of the authority, Mr. L~ws undertook the superintendence of the work, which is now nearly completed, and will be available in the event of a return of cholera this summer. Mr. Warner's technical description of the apparatus is as follows: The hulk measures fiftyfour and a-halt feet extreme length, and eighteen and a.half feet extreme breadth. The available space for machinery and storage is twenty-nine and a-quarter feet long by eighteen feet wide, forming the hold. The deck is continuous along the sides about two feet wide and at the fore and aft about twelve feet by twelve feet. The disinfecting apparatus consists of two circular tanks for solution of perchloride of mercury, each five and a-half feet in diameter b y four feet deep, together having a capacity of about i,~oo gallons. A steam disinlector three feet diameter by five feet six inches long, with the usual fittings to allow steam to pass into the materials under treatment, a steam pressure guage to register the temperature and pressure. The air compressor is of the vertical type, has steam cylinder four inches diameter by three-inch stroke, with air compressing cylinder five inches diameter by three-inch stroke. It is provided with fly-wheel and crank shaft to give even speed and regulate length of stroke. The air inlet and outlet valves are gun metal. The compressed air is conveyed to an air receiver two feet diameter by five feet high, made of steel boiler plates to form a reservoir of air at a pressure. The steam boiler is vertical type of four.horse power, six feet high by three feet diameter, having internal fire-box and two cross tubes. It is provided with steam pipes and connected with the air compressor on one side and the steam disinfector on the other. The boiler is capable of working at a pressure of 6o lbs. on the square inch, but a less pressure is found sufficient to work the ai r compressor and the disinfector. When working, steam is got up in the boiler and then passed by opening a valve into the pipes, so that clothing may be disinfected as desired by steam, but in order to use the perchloride of mercury spray the air compressor is started and allowed to compress air to about io lbs. pressure inside the air receiver. The compressed air supply pipes connect between the air receiver and two special spray nozzles, and they are also
S~tpplement to "' Public Health," J~dy,
189~.
Fw~. 1. --~EWCtSTLE (]ItOLERA STERILIZER..
F~G, S.--DISII~FEOTII~G H U L K
O F T H E B~IVER T Y N E POI~'~ S A N I T A R Y A U T H O R I T Y .
SEWER
AIR
INVESTIGATIONS.
connected to the bottom of the perchloride storage tanks. When the spray is used the compressed air passes down a double pipe conveying it along with the solution, and they meet together at the nozzle, where the force of air forms a spray at a pressure sufficient to carry several feet, and thus the decks and internal parts of an infected vessel may be easily covered with a fine spray of solution of perchloride of mercury. The estimated cost of the hulk and machinery complete is .£745. T h e accompanying illustration is from a photograph of the model.
SEWER AIR INVESTIGATIONS. Mtt. J. PARRY LAWS, F.I.C., has made, on behalf of the London County Council, two series of experimental observations on the condition of sewer air in London. T h e positive results of the first series of experiments are summarised by him as fallows : - I. T h e micro-organisms in the sewer air are related to the micro-organisms in the air outside, and not to the micro-organisms of the sewage. I I . In the air both within and without the sewer the forms of micro-organisms present are almost exclusively moulds and micrococci; on the contrary, the micro-organisms of sewage are for the most part bacilli. Of the latter sometimes as many as 2 5 per cent. very rapidly liquefy the gelatine on which they grow, whereas in the whole course of my experiments with fresh air and sewer air I only met with one colony, and that a micrococcus rapidly liquefying gelatine. I I I . That for purposes of deodorising, manganate of soda and sulphuric acid and carbolic acid are the most efficient of the several chemicals tried, and setting aside the question of relative cost, the former is decidedly preferable for the reason stated above. T h e whole of my results point unmistakably to the conclusion that the principal, if not the only, source of micro-organisms in sewer air is the air without the sewer and not the sewage, and they also tend to prove that there is very little ground for supposing that the micro-organisms of sewage, in the absence of violent splashing, become disseminated in the sewer air. Mr. Laws a d d s : In carrying out this work I have made a very large number of cultivations of the various organisms met with, in order to study them with the microscope both in stained and unstained specimens. I t is in this particular direction that my experiments are so much more complete than those of Drs. Carnelly and Haldane. I n conclusion let me emphasise the fact that these observations only hold good for sewers in
34 r
which the conditions are the same as those under which I experimented. What the condition of the air would be in sewers in which there is only an intermittent flow of sewage, or in which the sewage becomes stagnant and highly putrefactive, further experiment alone can show. T h e second report deals with experiments directed to ascertain the following points : - L Whether an increase in the velocity of the air current in a sewer beyond the limits met with under ordinary conditions would produce a concomitant increase in the number of microorganisms. 2. Whether the conclusions arrived at from the experiments in large sewers hold good for small sewers when the flow of sewage is intermittenh and the velocity of the air-current variable. 3, What influence, if any, stagnant and highly putrescent sewage has upon the number of microorganisms in sewer air. 4. Whether the various micro-organisms collected from sewer air during the progress of all my experiments were identical with the micro-organisms isolated from flesh air in the same vicinity and at the same time. T h e result conclusively showed that a considerable increase in the velocity in the air-current does not produce an increase in the number of microorganisms found in the sewer air. On the second point " i n most cases, under the conditions named above, the number of microorganisms found in the air surrounding the sewer exceeds those found in ~he air within ; in the only case in which the number of micro-organisms found within the sewer exceeds in a marked degree the organisms found without, the increase is entirely due to moulds, and not to bacteria. It is really remarkable to find that n o organisms are given off from the walls of a sewer which has been empty and open to the air at both ends for such a lengthened period as twelve d a y s The sewage with which the sewer had been kept full for several periods of twenty-four hours would contain no less than three to four million organisms per cubic centimetre, and immense numbers of these must of necessity have been clinging to the walls of the sewer. From this it is evident that the conclusions arrived at from my previous experiments in the King's Scholars' Pond sewer hold good for smaller s e w e r s , ~'
On the third point, the increase of microorganisras was found to be in moulds and not in bacteria. Mr. Laws summarises his general conclusions in the following words : - " T h e organisms of fresh air and sewer air were found to consist chiefly of moulds and micrococci, whereas the organisms ot sewage, so far as my limited observations go, consist essentially of moulds and bacilli. I have found the ratto of
CHOLERA
rain has been recognised by the New York Health Department, who have issued a circular ~ to medical men there explaining the arrangements made for this purpose. They say : " The differential diagnosis between true and false diphtheria can be made by bacteriological examinations within twelve hours, while without their assistance it is difficult or impossible. The Health Department is now prepared to make use of bacterial cultures in all cases of suspected diphtheria." The circular then proceeds to say that the medical man in charge may obtain the necessary culture tube free of cost from various centres, to which he will return it after inoculating it from the suspected throat, and the tubes will be daily sent on to the department from the local centre, or an officer of the board on receiving a request will attend and make the inoculation. By noon on the following day the medical man receives the result of the culture by telephone or through the post. There is no reason why this example should not be followed in this country. The expense of carrying it out would be trifling compared with the outlay entailed when a throat affection is true diphtheria, or is supposed to be so. I n London the Metropolitan Asylums Board would be the proper authority to take this matter up, and arrangements might be made with some central bacteriological laboratory to provide the culture tubes and make the cultivations. A supply of tubes might be kept at the of~ces of the boards and vestries, and each medical officer of health would deliver them to medical men applying, and would receive the report of the bacteriologist next day and convey it to the medical man in charge. But I would go further than this, and require that no case should be allowed to be removed from isolation, either in hospital or at home, until it had been proved that the throat were free of the bacillus, because it has been shown that virulent diohtheria bacilli may be found for an indefinite time after the apparent cure of the malady, and infection may be spread thereby. Especially in cases treated at home, I am inclined to the opinion that the patients are allowed to mix with healthy person at too early a stage, but, without the definite evidence given by finding the bacilli still there, it would be difficult for a medical man to insist on further isolation when the patient was to outward view apparently well. If diphtheria is to be stamped out, I feel sure that greater insistance must be laid on this point before disinfection of premises and clothing are caxried out. CONFERENCE ON SMALL-POX AND VAGRANTS,T h e Public Health Committee of the London County
Council have decided to convene a conference of urban sanitary authorities, to be held during July at Spring Gardens, to consider whether any measures can be taken to restrict vagrants as agents in the spread of small-pox and other infectious diseases. * "Journal of Laryngol0gy," October, I893.
STERILIZER.
339
INCORPORATED SOCIETY OF MEDICAL OFFICERS OF HEALTH. 2II"eetingof Memb.'rs, May zlst, x894. NEWCASTLE CHOLERA
STERILIZER.
DR. HENRY E. ARMSTRONG exhibited a model of the sterilizers provided by the sanitary authority of Newcastle.upon.Tyne for the hospital which they erected last year in anticipation of an outbreak of cholera, and said the Society had some time ago brought before them by Dr. Sisley a description, with drawings, of the cholera excreta sterilizer at the Alexander Hospital, St. Petersburg. That apparatus, though excellent in principal and original in design, was too elaborate and too costly for general use. It consisted essentially of a lareg central receiver, to which the excreta were conveyed by pipes from the different wards for subsequent sterilization in a steam jacketed boiler. These pipes--which in a large hospital would be of very considerable length:--together with their inlets, would be continually lined by a layer of infected excreta. There were also electric and other complicated appliances connected with the sterilizer which would be liable to get out of order. These objections were obviated in the cholera sterilizer, of which the exhibit is a model. Five of the sterilizers had been made for the Newcastle Cholera Hospital erected last summer. They were manufactured by Messrs. Goddard, Massey, and Warner, Nottingham, on the design of Mr. Wm. Warner, of that firm, acting under the instruction of the City Engineer of Newcastle-upon-Tyne, Mr. W. George Laws, M lnst,C.E, and the Medical Officer of Health. The apparatus, of which an illustration is given, consists of a ~o-gallon cast-iron sterilizing vessel, having in its top side a circular opening nine inches in diameter, with a hinged and balanced lid capable of being closed and made steam-tight. Communicating with the interior of the vessel are four pipes, viz., (i) a steam supply pipe, terminating near the bottom of the vessel, for sterilizing; (2) a steam eject pipe, terminating in the upper part of the vessel; (3) a water pipe for washing o u t ; and (4-) a pipe four inches in diameter for the discharge under steam pressure of the contents of the vessel after disinfection. The sterilizer is not jacketed. Its capacity is based on the estimated requirements of a ward of twenty beds. It is placed in an offshoot of the ward, corresponding to the chamber of a water closet. Into it are emptied tide evacuations, floor washings, and slops of all kinds. The exhibitor had had the idea of having the circular opening sufficiently large to admit a bed pan, but this was thought by Mr. Laws to be likely to weaken the apparatus, and was not attempted. The inlet is arranged to serve as the seat of a closet for convalesce~ts, and a wooden rim is provided for l~ying over it before such use. Z 2
34 °
D I S I N F E C T I N G H U L K OF R I V E R TYNE PORT SANITARY A U T H O R I T Y .
The modus aperandi is as tollows : Whenever the sterilizer is sufficiently full to be ready for disinfection, which may be once or twice every hour, an attendant is summoned, and enters the closet by an external door. He then fixes down the lid by means of the screws, and turns on steam for disinfection. In about seven minutes the pressure rises to 30 Ibs. After ten minutes more he opens the cock of the steam ejector, and closes that of the steam pipe for disintecting. He next opens the discharge valve, and the contents of the sterilizer are ejected into the tank, there to cool before being sent into the sewer. The cost of the sterilizers, apart from the steam appliances, is .~3o each. DISINFECrING [~IULK OF THE R I V E R T Y N E PORT
SANITARY AUTHORITY, The difficulty recently experienced in dealing with ships arriving from infected ports, and especially those infected with cholera, has created a need for more complete means of disinfection of vessels and their contents throughout than has hitherto been employed. During the cholera prevalence of the past two autumns the River Tyne Port Sanitary Authority, whilst fully appreciating the importance of the thorough disinfection of infected ships and their contents, has realized the inefficiency of the ordinary means and appliances. The Holt system, named after its organizer and developer, and cmTied out by him at New Orleans, has probably been hitherto the best in the world. The disinfection by steam and perchloride of mercury, in that system, is excellent. But the wholesale burning of sulphur, which is the third part of the system, is attended with risk of fire, and is otherwise open to objection. Apart from the mere difficulty of finding an available site for a disinfecting station on the shore of a port, the propriety of having such a fixed station in m o s t English ports is, to say the least, doubtful. In comparatively narrow river ports the danger to the floating and riparian populations of permitting an infected or suspected ship to pass upwards is sufficiently obvious. Besides, the free use of perchloride of mercury for disinfecting ballast and bilgewater in the upper reaches of such ports will poison the fish, a special objection in salmon streams Iike the Tyne. The use of liquefied sulphurous acid instead of burning sulphur does away with danger from fire. The objections to a disinfecting station fixed on land are obviated by the provision of a floating one to go to the infected ships instead of having them brought to it. The excellence of this suggestion, for which we are indebted to Mr. W. George Laws, C.E., was at once recognised by the writer and recommended to the Port Sanitary Authority, who approved and adopted the proposal. Messrs. Goddard, Massey, and Warner were invited to
prepare plans and estimates for a complete set of disinfecting apparatus in accordance with the report of the Medical Officer of Health, and the proposals of Mr. Laws, including (i) a steam disinfector for clothing, bedding, rags, etc. ; (2) apparatus for effectually douching decks, floors, woodwork, sand ballast, certain cargoes, etc., with a i-5oo solution of perchloride of mercury ; and (3) a plentiful store of liquefied sulphurous acid for fumigating berths, crew spaces, 'tween decks, or other infected places on shipboard. The plans were adopted, the machinery was ordered, a hulk was purchased to hold it, and on the request of the authority, Mr. L~ws undertook the superintendence of the work, which is now nearly completed, and will be available in the event of a return of cholera this summer. Mr. Warner's technical description of the apparatus is as follows: The hulk measures fiftyfour and a-halt feet extreme length, and eighteen and a.half feet extreme breadth. The available space for machinery and storage is twenty-nine and a-quarter feet long by eighteen feet wide, forming the hold. The deck is continuous along the sides about two feet wide and at the fore and aft about twelve feet by twelve feet. The disinfecting apparatus consists of two circular tanks for solution of perchloride of mercury, each five and a-half feet in diameter b y four feet deep, together having a capacity of about i,~oo gallons. A steam disinlector three feet diameter by five feet six inches long, with the usual fittings to allow steam to pass into the materials under treatment, a steam pressure guage to register the temperature and pressure. The air compressor is of the vertical type, has steam cylinder four inches diameter by three-inch stroke, with air compressing cylinder five inches diameter by three-inch stroke. It is provided with fly-wheel and crank shaft to give even speed and regulate length of stroke. The air inlet and outlet valves are gun metal. The compressed air is conveyed to an air receiver two feet diameter by five feet high, made of steel boiler plates to form a reservoir of air at a pressure. The steam boiler is vertical type of four.horse power, six feet high by three feet diameter, having internal fire-box and two cross tubes. It is provided with steam pipes and connected with the air compressor on one side and the steam disinfector on the other. The boiler is capable of working at a pressure of 6o lbs. on the square inch, but a less pressure is found sufficient to work the ai r compressor and the disinfector. When working, steam is got up in the boiler and then passed by opening a valve into the pipes, so that clothing may be disinfected as desired by steam, but in order to use the perchloride of mercury spray the air compressor is started and allowed to compress air to about io lbs. pressure inside the air receiver. The compressed air supply pipes connect between the air receiver and two special spray nozzles, and they are also
S~tpplement to "' Public Health," J~dy,
189~.
Fw~. 1. --~EWCtSTLE (]ItOLERA STERILIZER..
F~G, S.--DISII~FEOTII~G H U L K
O F T H E B~IVER T Y N E POI~'~ S A N I T A R Y A U T H O R I T Y .
SEWER
AIR
INVESTIGATIONS.
connected to the bottom of the perchloride storage tanks. When the spray is used the compressed air passes down a double pipe conveying it along with the solution, and they meet together at the nozzle, where the force of air forms a spray at a pressure sufficient to carry several feet, and thus the decks and internal parts of an infected vessel may be easily covered with a fine spray of solution of perchloride of mercury. The estimated cost of the hulk and machinery complete is .£745. T h e accompanying illustration is from a photograph of the model.
SEWER AIR INVESTIGATIONS. Mtt. J. PARRY LAWS, F.I.C., has made, on behalf of the London County Council, two series of experimental observations on the condition of sewer air in London. T h e positive results of the first series of experiments are summarised by him as fallows : - I. T h e micro-organisms in the sewer air are related to the micro-organisms in the air outside, and not to the micro-organisms of the sewage. I I . In the air both within and without the sewer the forms of micro-organisms present are almost exclusively moulds and micrococci; on the contrary, the micro-organisms of sewage are for the most part bacilli. Of the latter sometimes as many as 2 5 per cent. very rapidly liquefy the gelatine on which they grow, whereas in the whole course of my experiments with fresh air and sewer air I only met with one colony, and that a micrococcus rapidly liquefying gelatine. I I I . That for purposes of deodorising, manganate of soda and sulphuric acid and carbolic acid are the most efficient of the several chemicals tried, and setting aside the question of relative cost, the former is decidedly preferable for the reason stated above. T h e whole of my results point unmistakably to the conclusion that the principal, if not the only, source of micro-organisms in sewer air is the air without the sewer and not the sewage, and they also tend to prove that there is very little ground for supposing that the micro-organisms of sewage, in the absence of violent splashing, become disseminated in the sewer air. Mr. Laws a d d s : In carrying out this work I have made a very large number of cultivations of the various organisms met with, in order to study them with the microscope both in stained and unstained specimens. I t is in this particular direction that my experiments are so much more complete than those of Drs. Carnelly and Haldane. I n conclusion let me emphasise the fact that these observations only hold good for sewers in
34 r
which the conditions are the same as those under which I experimented. What the condition of the air would be in sewers in which there is only an intermittent flow of sewage, or in which the sewage becomes stagnant and highly putrefactive, further experiment alone can show. T h e second report deals with experiments directed to ascertain the following points : - L Whether an increase in the velocity of the air current in a sewer beyond the limits met with under ordinary conditions would produce a concomitant increase in the number of microorganisms. 2. Whether the conclusions arrived at from the experiments in large sewers hold good for small sewers when the flow of sewage is intermittenh and the velocity of the air-current variable. 3, What influence, if any, stagnant and highly putrescent sewage has upon the number of microorganisms in sewer air. 4. Whether the various micro-organisms collected from sewer air during the progress of all my experiments were identical with the micro-organisms isolated from flesh air in the same vicinity and at the same time. T h e result conclusively showed that a considerable increase in the velocity in the air-current does not produce an increase in the number of microorganisms found in the sewer air. On the second point " i n most cases, under the conditions named above, the number of microorganisms found in the air surrounding the sewer exceeds those found in ~he air within ; in the only case in which the number of micro-organisms found within the sewer exceeds in a marked degree the organisms found without, the increase is entirely due to moulds, and not to bacteria. It is really remarkable to find that n o organisms are given off from the walls of a sewer which has been empty and open to the air at both ends for such a lengthened period as twelve d a y s The sewage with which the sewer had been kept full for several periods of twenty-four hours would contain no less than three to four million organisms per cubic centimetre, and immense numbers of these must of necessity have been clinging to the walls of the sewer. From this it is evident that the conclusions arrived at from my previous experiments in the King's Scholars' Pond sewer hold good for smaller s e w e r s , ~'
On the third point, the increase of microorganisras was found to be in moulds and not in bacteria. Mr. Laws summarises his general conclusions in the following words : - " T h e organisms of fresh air and sewer air were found to consist chiefly of moulds and micrococci, whereas the organisms ot sewage, so far as my limited observations go, consist essentially of moulds and bacilli. I have found the ratto of