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On disinfection by steam derived from saline solutions
D I S I N F E C T I O N BY STEAM D E R I V E D FROM S A L I N E SOLUTIONS. Coming to causes of mortality, Mr. Hoffman finds that the coloured race, as compared with the white, have an excessive mortality, from all diseases, of infants; from phthisis especially, at the ages i5-45; from venereal diseases; from malarial fevers, contrary to general opinion ; and from some other diseases. " I n the struggle for gace supremacy the black race is not holding its own Its extreme liability to consumption alone would suffice to seal its fate as a race. That alone would suffice to make impossible numerical supremacy in the Southern States." In the chapter on Anthropometry, the close relationship between weight of the individual and longevity is brought out, a number of elaborate tables showing this being given. Doubtless it acts through the predisposition to phthisis thus indicated ; but, whatever the reason, its importance for insurance purposes is obvious. The chapter on Race Amalgamation is extremely interesting. It is full of information on a difficult subject. The American people have shown themselves able to absorb and assimilate the European immigrants, however numerous they may be. Contrary to expectations, however, there has been no general fusion of the coloured and white races. This is not desirable, even from the standpoint of the negro. The Mulatto (like the Eurasian) may be higher intellectually than his coloured ancestor, but he is a degenerate, physically. Analogous cases prevent one from expecting in the future any such amalgamation of the white and coloured races. ~"[er marriages between Lapps and Swedes, and between Lapps and Russians, are very rare. The Ainos of Japan, who are a distinct race from the Japanese, remain, after centuries of close association, perfectly distinct. The facts as to the low state of sexual morality among the coloured population are sad reading. The state of things is shown, for instance, by the fact that, in 1879-94 , the percentage of illegitimate to total number of births in Washington, was 2"92 among the white, and 22"49 among the coloured population. A still more striking fact is that, during this period, the illegitimate births among the whites were, from 2"32 in 1879, to 2'56 in I894 , while among the blacks they increased from 17"60 to 26"46. With Mr. Hoffman's final conclusions a hearty agreement may be expressed. The decadence and gradual extinction of the Maoris and the Red Indians are alike traced to the unchastity and consequent syphilitic affections connected with promiscuous sexual intercourse. So, likewise, the lack of self-reliance and chastity of the coloured race are working towards a similar end. These downward tendencies "can only be arrested by radical and far-reaching changes in their moral nature. Instead of clamouring for aid from the white race, the negro himself should sternly refuse every offer of direct interference in his own evolu-
99
tion . . . Most of all there must be a m o r e general recogniti4m of the institution of monogamic marriage, and unqualified reprobation of those who violate the law of sexual morality. Intercourse with the white race must cease, and race purity must be insisted upon in marriage as well as outside of it." We have touched on only a few of the interesting race problems, discussed with interesting and accurate detail by Mr. Hoffman. Enough has been said, however, to commend his work as a most valuable and substantial contribution towards a problem of vital interest to all who have the wider interests of the human race at heart.
ON D I S I N F E C T I O N BY STEAM D E R I V E D FROM SALINE SOLUTIONS. BY
WOLF DEFRmS, B.A. Lond., M.I.Mech.E. TO avoid misunderstanding, it wilt be convenient to state the meaning of some terms used in regard to steam in disinfection practice. t. Confined Steam means steam retained i n n dosed chamber. Current Steam means steam in motion. 2. Non-2ressure Steam means steam at the pressure of the atmosphere. Steam Under Pressure means steam at a higher pressure than that of the atmosphere. It can exist and is used, as is non-pressure steam, either confined or as a current. 3. Saturated Steam means steam at the temperature at which it can condense: This temperature depends on the pressure. For each pressure there is only one temperature at which steam can condense; for example, at normal barometric pressure steam can only condense at IOO° C. The con, densing point rises as the pressure increases, and by sufficiently increasing the pressure saturated steam can be obtained of any temperature whatever. When saturated steam condenses, it shrinks into about one sixteen.hundredth of its own volume of water at the same temperature ; and the energy which had previously been employed in retaining it in the form of vapour is given off in the form of heat. It i~ therefore said that steam contains latent heat. The amount of heat so contained by steim, and given off by it in condensing without loss of temperature, is sufficient to raise the temperature of ioo times its weight of wool by about I5~ to 16 ° C. The communication of heat to objects during steam disinfection is due almost entirely to this evolution of latent heat. Superheated Steam means steam at a temperature higher than that at which it can condense. It can exist at any pressure ; but the temperature does not correspond to the pressure, for it is impossible by measurement of temperature to say how much of the heat in the steam is occupied in preventing the steam from condensing under the pressure,
too
D I S I N F E C T I O N BY STEAM D E R I V E D F R O M S A L I N E SOLUTIONS.
and how much has been added from external sources. Superheated steam by definition cannot condense until it has been cooled down into the state of saturated steam. This cooling is effected by conduction, whereby the steam falls in temperature by, roughly, about the same number of degrees as that by which it raises its own weight of wool. Superheated steam and wool are both bad conductors, and this process is therefore slow, unless the wool is much colder than the steam. The amount of heat which can be communicated in this cooling by conduction is also insignificant compared with that instantaneously given off in condensing. When superheated steam is used for disinfection, practically all the heating effect is due to the action of the steam after it has been cooled into saturated steam. I have given these descriptions, familiar as they are, in detail, because they are frequently overlooked in discussions of the subject. In the paper, for instance, in last month's PUBLIC HEALTH, by Dr. Mearns Fraser, on " T h e Thresh Disinfector," they are for the most part ignored. In consequence, Dr. Fraser divides methods of steam disintection into those using respectively superheated steam, steam under pressure, and current steam. From the definitions of the terms it is obvious that steam can exist in all three states, or in any combination of two of them at the same time; and, in point of fact, well-known machines have been made to be used respectively with steam in each of these four combinations. Thedisinfector, for example, described in Dr. Fraser's paper, uses steam which is at once superheated and current steam. The confusion of thought which must arise from such a classification can perhaps be realised better by contemplating the discussion of water under the headings of cold water, soft water, and well-water. It must accordingly be clearly realised that the anh'thesis to sul)erheated steam is saturated steam; to steam under ~ressure, is non-lOressure steam ; and to current steam, is confined steam.
It may be taken, as Dr. Fraser has said, that the use of superheated steam cannot be seriously supported. It has been definitely established that even on naked organisms its disinfectant value is much lower than that of saturated steam, and, as follows from the description of its behaviour in cooling, it is likewise very much slower in its penetration into objects. It is rsometimes forgotten that steam raised from saline solutions having a boiling point higher than that of water--the kind of steam contemplated in this article--is necessarily superheated. The reason is that it is the water in the solution and not the solution itself which is converted into steam. Accordingly the operation of boiling such solutions requires heat both for separating the water from the salt, and for converting the water into steam. The steam then becomes of the temperature to which the solution is raised by this amount of heat. It has
therefore received a larger amount of heat than is required to prevent it from condensing ; and until this excess of heat is removed, it cannot condense into water at the lower temperature necessary for condensation. In practical disinfection this only becomes a conclusive objection when the amount of superheat is such as to prevent the steam from being rapidly cooled to saturation. It hay, however, the disadvantage of increasing the time of penetration by an extent corresponding to the extent of the superheat ; though in disinfectors working at only a few degrees of superheat this may often be only a small matter. In the case, however, of disinfectors having a few degrees of super. heat, and working at or about the death-temperature of the organisms, it becomes a serious matter, the final few degrees of heat which are communicated from the superheated steam by the slow process of conduction being essential to the disinfection. The use of saline solutions accordingly entails the disadvantages and risk inseparable from superheated steam, and it depends upon various circumstances whether these objections, inevitably present to a greater or ~ess extent, are sufficiently grave to be fatal. The purpose for which their use has been suggested is the construction of cheap disinfectors for village and similar communities, where the expense of a dismfector working with steam under substantial pressure cannot be borne ; and the particular method of application which has been recommended for the purpose is that of current steam without pressure. For present practical purposes, accordingly, it is chiefly important to consider the efficiency of disinfectors working with steam in this state. It has recently been suggested that curi'ent steam without pressure penetrates objects more rapidly, and disinfects more efficiently, than steam under pressure. A statement to this effect occurs in Dr. Fraser's paper (PUBLIC HEALTH, October, i896 , P. 5), and the same statement has recently appeared elsewhere. The proposition amounts to thisuthat the hotter steam becomes, the less capable it is of heating objects in contact with it. This paradox was first stated by Koch in 188t. It was inconsistent with the experience of N~igeli and his pupils since I87o , and afterwards Koch's report was investigated by Buchner, Fitz, and others, who were unable to obtain the same results as Koch. The matter was ultimately cleared up by Heydenreich, in I884. He found that Koch's results could only be reproduced so long as a certain amount of air was mixed with the steam. Numerous independent instances of the inaccuracy of the statement were found. Globig killed dried spores by ten minutes' exposure to saturated steam under pressure at I2o°C., while they resisted five or six hours of current steam without pressure ; Gruber killed other spores with twenty minutes' exposure to saturated steam under pressure at x io°C., while they not only survived, but appe~ed to suffer no
DISINFECTION
BY STEAM
DERIVED
attenuation of any kind after exposure to current steam without pressure for two and a-half hours. Kitt, using symptomatic anthrax spores in dried muscle's~ found the organisms to survive six hours of current steam without pressure~ and to yield to twenty minutes of saturated steam under pressure at IIo°C. Quite recently Miquel rein,,estigated the whole question of the temperature proper ,for steam disinfection, his experiments being the most precise of any which I know on the subject of thermal death-points with steam ; and he found equally that 2o minutes at 1 Io?C. was indispensable for safety, and that no reasonable or practieable exposure, whether continuous or otherwise, to current s,eam without pressure was adequate. The proposition that current steam without pressure has a higher disinfecting power than ,aturated steam under pressure is, therefore, not only inaccurate, but has been known since i884 to express the exact contrary of the truth. It is precisely the same with the proposition that steam under pressure penetrates more slowly into porous objects than current steam without pressure. Many observers, in comparing different machines, found the exact contrary, notably Salomonsen and Levison. Budde worked with one machine at various pressures, and found that the higher the pressure the more the heat penetrated into objects. Pfuhl, using a machine of another construction at various pressures, obtained precisely the same result. Frosch and Clarenbach took the pressures up successively from one-fortieth to one-fifth of an atmosphere, and found that as the pressure increased so did the rate of penetration. In the whole collection of serious experiment on the subject which has been made in the last ten years, I know of no case in which current steam without pressure has given as good results~ either in point of penetration or of disinfection, as in like conditions has been given by steam under pressure. It is accordingly needless to occupy space in discussing the hypothesis by which Dr. Fraser thinks that the alleged inferiority of steam under pressure may be explained. Steam without pressure does not penetrate or disinfect so quickly as steam under pressure, and disinfectors working with it must be used, if at all, with proper regard to this fact. There is, however, a more serious objection to this method of using steam for disinfection. Not only the temperature obtained, but also the rate of disinfection varies with the velocity of the steam, i.e., with the way in which the fire is stoked. This was accidentally discovered by Esmarch, in Ig87, and thereafter verified by him in deliberate experiments. It has been confirmed wherever it has been examined in later years, down to the inquiry of the present year by Dr. Smith. Accordingly the temperature and the rate of disinfection in disinfectors working with current steam without pressure will vary with the energy of the attendaut, the nature of the coal,and similar circumstances
FROM
SALINE SOLUTIONS.
xox
entirely beyond the control of the responsible medical officer. I am confirmed in regarding this as a serious objection to the use of steam in this way, because, if anything is settled in regard to steam disinfection, it is that the operation shall as far as possible be made the subject of automatic control. This control can practically only be obtained by using saturated steam under some pressure capable of being recorded on a recording pressure-gauge. Where cheapness is absolutely indispensable this pressure is sometimes reduced to as little as one-twentieth of an atmosphere. The absence of some pressure by which the temperature of the steam can be known and controlled is, in the light of modern practice, a fatal obiection to the use of current steam without pressure. Apart from the control which is impossible without pressure, it is desirable to recognise that absolute disinfection cannot be assured without temperatures higher than can in practice be yielded by steam without pressure. It will be remembered that even where saline solutions are used, they cannot be allowed to give a temperature much higher than boiling point, for fear of increasing the risk due to the presence of superheat. In connection with the apparatus described by Dr. Fraser, it is stated that pathogenic organisms are infallibly destroyed by exposure to steam at 2~2 ° F. for five minutes. The statement in question is in t~o senses inaccurate. It is contradicted directly by facts that are known ; and it makes an assertion about things that are not known. The organism of symptomatic anthrax has repeatedly been shown, as in the experiments of Kitt, quoted above, to resist many hours' exposure to 212 ° F. Grancher and LedouxLabard have boiled tuberculous matter for one hour, and a second portion for three hours; in each case finding that the infection retained its virulence, the test-animals dying at lengths of time correspondin~ with the extent to which the matter had been boiled. I could multiply instances indefinitely, which directly contradict the proposition which I have quoted. It is ~aid, sometimes, that these are not the diseases against which we disinfect, and that if they were~ their organisms have been destroyed by lesser exposures. If, unfortunately, it be true that disinfection after and during tuberculosis is not yet usual in this country, as it is in America and elsewhere, it is to be hoped that this reproach may not continue for long ; and it does not alter the fact that some British authorities already practise it. That organisms perish at variable temperatures depending on all sorts of partly-known circumstances in their life-history is common knowledge, and the fact that some specimens of an organism have perished at a lower temperature does not alter the fact that other specimens have survived the higher temperature~ and may at any time do so again, But the proposition is al.~o inaccurate through the fact that o~ some infectiousdiseases,as small-pox and
tO2
D I S I N F E C T I O N BY STEAM D E R I V E D FROM SALINE SOLUTIONS.
seadet fever, the existing organism is not yet demonstrated; and that no "infallible" knowledge, and no knowledge at all of which account can be taken scientifically, exists as to the resistance of these unknown organisms to disinfection by steam. It has been suggested that they would probably follow the analogy of organisms such as those of typhoid fever and diphtheria, and perish below too ° C. It is equally conceivable that they may take the course of symptomatic anthrax, tuberculosis, and other organisms pathogenic and otherwise, and require much higher temperatures. Analogy, indeed, for what it may be worth, is rather in favour of the latter hypothesis. The circumstance pointed out in last month's _PUBLIC HEALTH,that the symptomatic anthrax organism may be preserved alive for at least ten years without loss of virulence, is singularly like the capacity of scarlet fever infection to persist for many years, and suggests the old native habit in India of successfully inoculating with the same piece of small-pox scab for an apparently indefinite time. A considerable responsibility is therefore undertaken by those persons who, in the face of these facts, use steam at or about ioo ° C., when they can procure the use of steam under adequate pressure. Nevertheless, where sufficient funds cannot be obtained, it is unquestionably better to use steam under very slight pressure than hot-air or sulphur chambers. I have set out the objections which exist to the use of current steam at atmospheric pressure. When this steam is derived from saline solutions, it is complicated by the disadvantages due to the presence of superheat. There are, however, other difficulties. Boilers in which steam is formed are liable to "prime," that is, to allow drops of water to be carried over by the steam. This phenomenon is usually most pronounced when the water contains impurities. I f this occurred in the use of saline solutions for disinfection, two consequences would follow. In the first place the strength of the solution, which no doubt would always be regulated by the admission of water up to a constant level, would vary, and with it the temperature of the steam. In the presence of the inevitable variations due to steam velocity, this would not be a matter of much importance in using current steam without pressure. But some of this liquid would naturally be absorbed by the objects under disinfection. This would not sensibly increase their weight after drying at the t i m e ; b u t with any deliquescent salt, such as calcium chloride, it would on exposure to an atmosphere not rigidly dry, serve to make ihe objects damp and to keep them so, unless the salt was washed out of them, a process which with many objects is practically impossible. I f there is any evidence to show that this priming, which would certainly be expected on generalgrounds, does not occur, I must say that I have not seen it. The same remark applies to the last objection which I
need mention to the use of saline solutions, that o n e would expect them after being used for some time, particularly when the use was discontinuous, to cause scale and ultimate corrosion of the boiler. I can therefore see no inducement, and can see considerable objection, to the employment of saline solutions for steam-raising in disinfection, and especially to the use of current steam without pressure derived from them. The matter does not, however, rest solely on the general considerations which I have set out. The use of saline solutions, suggested by Koch, in i88I, was actually carried out some two or three years later by Professor Dobroslavin, and a little afterwards by Dr. Emme. Dobroslavin's arrangement, the well-known ltu~e selhydriCue, consisted of a disinfecting chamber surrounded by a closed jacket. The solution was contained in the lower part of the space between the chamber and the jacket, and the steam, formed in the upper part of the same space, was conducted down in pipes through the hot solution, and thence led up into the disinfecting chamber. This arrangement, as will be seen by reference to Dr. Fraser's paper, is substantially the same as that which was recentlymI need not say quite independently-invented by Dr. Thresh ; and it certainly appears to give the steam every chance of doing its best. Disinfectors were made on this design, and used for some years. The net upshot was stated by Dobroslavin himself at the Congress of Vienna. He had found it necessary to abandon altogether the use of saline solutions, and had been able to do better with the disinfector by the use of ordinary water. In conclusion, I desire to point out that the considerations which I have discussed do not affect one or several disinfectors, but all steam disinfectors. If saline solutions were advantageous, they could be used by every authority possessing existing disinfectors. Every maker of such appliances could either adopt Dobroslavin's arrangement as it stands, or could modify it so as to retain any features in his existing appliances which he considered advantageous, or to provide such pressure as he might be advised was desirable. Contrariwise, any arrangement which was good for use with steam derived from saline solutions would serve with equal advantage for use with ordinary steam. I refer to the general nature of the discussion, because some people in this country have apparently a difficulty in realising that the discussion of the general principles involved in the construction of sanitary appliances is not necessarily equivalent to a recommendation of one or other machine. Such discussions, as distinguished from the bare recital of advantages attributed on the basis of sporadic experiment to individual appliances, have for many years been constantly going on abroad; and, in particular, they have largely contributed to form the data on which the construction and use of steam disinfectors should be based.
SERUM-DIAGNOSIS OF T Y P H O I D FEVER. SERUM-DIAGNOSIS OF T Y P H O I D FEVER. THE Board of Health of Quebec have taken an important step in regard to the diagnosis of typhoid fever, as wilt be seen from the circular, the substance of which we append. The practical result of this method of diagnosis will be watched with great interest ; and it need hardly be said that if the method of serum-diagnosis here set forth affords a means of ready and early diagnosis, it will furnish a substantial addition to the armament of preventive medicine : " T h e Board of Health of the Province of Quebec desires to call the attention of the medical profession and sanitary authorities of this Province to the fact that bacteriological methods seem hkely to afford a rapid and satisfactory method of diagnosis in typhoid fever, which will compare not unfavourably in point of efficiency with the methods now so widely employed for the diagnosis of tuberculosis and diphtheria. " I t has been shown by Pfeiffer of Berlin and Widal of Paris, that the serum obtained from the blood of a typhoid fever patient is capable of so acting upon pure bouillon cultures of typhoid bacilli mixed with it as to abolish the active motion so characteristic of that organism in fluid culture media, and cause an agglutination of the individual bacilli into large groups or clumps. This change is easily recognizable under the microscope--or in culture tubes--and usually occurs within a few minutes. "With serum from the blood of healthy persons or those suffering from febrile diseases other than typhoid, the motion of the bacilli is not arrested, but continues indefinitely when mixed with the typhoid culture. " T h e method as originally introduced by Pfeiffer involved somewhat difficult and complicated procedure for obtaining pure and sterile serum, but the process has recently been much simplified by Widal, who found that a few drops of blood collected in a sterilized glass tube, suffices for the test. c, Widal and Sicard state that the serum and blood, when dried, retain their power of producing this effect, though they do not record any practical application of this circumstance. " I t has been since shown by Dr. Wyatt Johnston, bacteriologist of this Board, that the fluid obtained by moistening with water a dried blood-drop gives the reaction in a prompt and satisfactory manner, even after it has been dried for several days. This modification of the process makes it more suitable for a system of free public laboratory diagnosis, similar to that in the case of diphtheria, as a drop of dried blood can be more readily sent to a laboratory and examined there. The bacteriolo gist of the Board was able to diagnose correctly by means of dried blood drops sent by mail from Montreal to Buffalo, N.Y., during the meeting of the American Public Health Association, in September, 1896 , those which were from typhoid
io 3
cases and those which were not, using no other means than the method described above. "As the subject is a new one, the Board does not feel in a position to state exactly what degree of accuracy will be obtained from this method, when used for the routine diagnosis of typhoid fever on a large scale, but in order to test the 2Oractt'calutility of the method, hereby offers to examine and report (gratis) upon any samples of blood collected by physicians of this Province, as directed in the instructions given with the outfits. A report will be sent by 2 p.m. upon the day following that upon which the sample is received, and will be communicated by telephone when the number is given. " T h e Board wishes to obtain data upon the following points, and earnestly requests the medical profession to aid them by furnishing any information bearing upon them :-" i. The proportion of cases in which a correct diagnosis can be made by the serum test, and the relative efficiency of the method of employing dried samples. "2. The earliest period in typhoid fever at which it can be expected to give indications. "3. The length of time for which it persists after convalescence. "4. The existence of any relation between the intensity of reaction with the test and the course of the disease. "5. The study ofthe nature of the obscure febrile conditions, clinically termed gastric fever, continued fever, abortive typhoid bilious fever~ typho-malarial fever, etc., about which our present knowledge is very meagre and unsatisfactory. " I t is hoped that those who take advantage of the offer now made by the Board will do all in their power to aid this inquiry by not only carefully filling up the blanks sent with the samples, but by afterwards giving information, when possible, as to whether the subsequent progress of the case confirmed the result of the serum test or not, and also by providing, when possible, temperature charts, etc., for study by the officials of the Board. " T h e Board is especially desirous of hearing promptly of and re-examining any genuine typhoid cases in which the method is not successful. In case of negative results, it is desired that the second time, an additional sample should also be sent, consisting of a few drops of blood collected in one of the glass tubes, which will be furnished on special application at the dep6ts. "With reference to the effect of drying the samples: while this may lessen slightly the delicacy of the reaction, it has the practical advantage of obviating, a serious source of error, namely, the contamination of the sample and the subsequent growth of putrefactive bacteria. This is of special importance in the case of samples having to be sent for long distances. "With regard to the significance of negativeresults, we may quote the following statement by Widal :
~o4
HEALTHY
,t, A negative result obtained with the serum of a case of suspected typhoid affords a presumption against the diagnosis of typhoid fever, but this is only a probability, especially if the examination has been made in the first few days of the disease. The examination should then be repeated during the next few days. The presumption that a case in which a negative result has been obtained is not typhoid, becomes correspondingly stronger as the stage of the disease becomes more advanced.'" HEALTHY MILK. DR. NIvE~, Medical Officer of Health of the City of Manchester, delivered a Lecture on the 9th ult. on " How a City may be Supplied with Good Milk," under the auspices of the Ancoats Healthy Homes Society. Dr. Niven said a vast number of children were swept away every year by diarrhoea, and the most searching enquiry showed that these deaths were directly caused by the milk on which the children were fed. This was often the fault of the mother by not taking the precaution to boil the milk, but it would not avail to boil the milk unless it arrived of sufficiently good quality. They could kill the living matter in the milk, but could not by boiling deprive it of its poisonous properties if it had become poisoned. Those injurious properties the milk too often acquired as soon as it came from the cow. Cows in a very large number of instances were infected with tubercular disease. In a certain proportion of cows, and practically in all when the udder had become tuberculou% the milk became infected, and was capable of giving children consumption of the bowels. Generally speaking, about twenty per cent. of the cows in this country were affected with this disease. Every now and then they also found widespread and disastrous epidemics of typhoid fever, scarlet fever, and diphtheria attributed to and clearly proved to have come from milk which had become infected, and they ought seriously to consider where it was a necessary thing for these evil consequences to accrue from the use of milk. About two years ago, Dr. Niven said, his attention was called to a pamphlet published by Mr. Stuart Macgregor, the British Vice-Consul in the Danish Capital, describing the system whereby they could have milk fragrant, pure, and clean. H e was sure every one would wRh that such milk should be brought into this community. I f milk were drawn from the cow on a summer day, and exposed a short time, a vast number of microorganisms developed, and caused changes in it which led to the production of elements that were poisonous to the human system. H e did not mean to say that all the milk used contained poisonous material, but that the milk used in summer was liable to contain such material. In August last, when he journeyed through Denmarl~ to Copenhagen, he found that the fields consisted
MILK. chiefly of red clover, and in these the cows grazed, and they were milked in the fields. H e went through one of the factories to which the milk was taken in cans--the employgs were compelled to put on clean cotton outer clothing as they came in to work--the milk was brought to the factory from the farms in railway trucks, and the cans were surrounded by ice, and the cows were periodically examined by the veterinary surgeons appointed by the company. They had one special quality of milk for the feeding of children, which was called "children's milk." For the supply of this they selected the best cows. The milk was tested by an expert, and if any of it was found to be in the sligh'est degree disagreeable, it was rejected. The cows were allowed no brewers' grains or turnips, but they were allowed carrots and beetroot. This special feeding was the result of careful experiment and scientific knowledge, and it was worthy of note that the chief food here was distinctly and absolutely excluded there. From the mqment of the milk leaving the cow, it was kept in a very low temperature, and as the cans or bottles left the factory for the consumer they were surrounded with ice. The company received the milk from fifty-seven large farms, each farm having from 5o to 20o cows. The total number of cows supplying the company last ~ear was 5,024, and the amount of milk supplied to the public in i894 was two million gallons. The farms he visited were beautifully clean, the floor was of concrete, and the cows were invariably littered with clean straw. The price in Denmark was ts. per gallon for the best milk, and he thought every one would agree, if they could get milk from English dairies protected in this manner, at a reasonable price, they would be conferring a great boon on the community, and he did not see any reason why it should not be done. S T E A M I N G IN C O T T O N W E A V I N G SHEDS
•
BY
EDWARD
SEROEANT, M.R.C.S., L.R.C.P., L.S.S.C., M.O.H. Lancashire.
THE agitation which has recently arisen against steam in certain districts of this countyj induced me to visit several weaving sheds in the Urban districts of Hurst and Padiham: and facilities have also been kindly extended to me for an examination of the conditions affecting weavers in the county boroughs of Blackburn and Preston. From personal knowledge of weaving sheds, extending over many years, I feel justified in saying that the working of the Cotton Cloth Factories Act, x889, has been productive of much good, and with few exceptions the limits of humidity allowed by the Act are faithfully adhered to. In the manufacture of heavily-sized cloth a high state of humidity seems to be necessary, and at the • From Annual Report, for I895, to the Lancashire County Council.
99
tion . . . Most of all there must be a m o r e general recogniti4m of the institution of monogamic marriage, and unqualified reprobation of those who violate the law of sexual morality. Intercourse with the white race must cease, and race purity must be insisted upon in marriage as well as outside of it." We have touched on only a few of the interesting race problems, discussed with interesting and accurate detail by Mr. Hoffman. Enough has been said, however, to commend his work as a most valuable and substantial contribution towards a problem of vital interest to all who have the wider interests of the human race at heart.
ON D I S I N F E C T I O N BY STEAM D E R I V E D FROM SALINE SOLUTIONS. BY
WOLF DEFRmS, B.A. Lond., M.I.Mech.E. TO avoid misunderstanding, it wilt be convenient to state the meaning of some terms used in regard to steam in disinfection practice. t. Confined Steam means steam retained i n n dosed chamber. Current Steam means steam in motion. 2. Non-2ressure Steam means steam at the pressure of the atmosphere. Steam Under Pressure means steam at a higher pressure than that of the atmosphere. It can exist and is used, as is non-pressure steam, either confined or as a current. 3. Saturated Steam means steam at the temperature at which it can condense: This temperature depends on the pressure. For each pressure there is only one temperature at which steam can condense; for example, at normal barometric pressure steam can only condense at IOO° C. The con, densing point rises as the pressure increases, and by sufficiently increasing the pressure saturated steam can be obtained of any temperature whatever. When saturated steam condenses, it shrinks into about one sixteen.hundredth of its own volume of water at the same temperature ; and the energy which had previously been employed in retaining it in the form of vapour is given off in the form of heat. It i~ therefore said that steam contains latent heat. The amount of heat so contained by steim, and given off by it in condensing without loss of temperature, is sufficient to raise the temperature of ioo times its weight of wool by about I5~ to 16 ° C. The communication of heat to objects during steam disinfection is due almost entirely to this evolution of latent heat. Superheated Steam means steam at a temperature higher than that at which it can condense. It can exist at any pressure ; but the temperature does not correspond to the pressure, for it is impossible by measurement of temperature to say how much of the heat in the steam is occupied in preventing the steam from condensing under the pressure,
too
D I S I N F E C T I O N BY STEAM D E R I V E D F R O M S A L I N E SOLUTIONS.
and how much has been added from external sources. Superheated steam by definition cannot condense until it has been cooled down into the state of saturated steam. This cooling is effected by conduction, whereby the steam falls in temperature by, roughly, about the same number of degrees as that by which it raises its own weight of wool. Superheated steam and wool are both bad conductors, and this process is therefore slow, unless the wool is much colder than the steam. The amount of heat which can be communicated in this cooling by conduction is also insignificant compared with that instantaneously given off in condensing. When superheated steam is used for disinfection, practically all the heating effect is due to the action of the steam after it has been cooled into saturated steam. I have given these descriptions, familiar as they are, in detail, because they are frequently overlooked in discussions of the subject. In the paper, for instance, in last month's PUBLIC HEALTH, by Dr. Mearns Fraser, on " T h e Thresh Disinfector," they are for the most part ignored. In consequence, Dr. Fraser divides methods of steam disintection into those using respectively superheated steam, steam under pressure, and current steam. From the definitions of the terms it is obvious that steam can exist in all three states, or in any combination of two of them at the same time; and, in point of fact, well-known machines have been made to be used respectively with steam in each of these four combinations. Thedisinfector, for example, described in Dr. Fraser's paper, uses steam which is at once superheated and current steam. The confusion of thought which must arise from such a classification can perhaps be realised better by contemplating the discussion of water under the headings of cold water, soft water, and well-water. It must accordingly be clearly realised that the anh'thesis to sul)erheated steam is saturated steam; to steam under ~ressure, is non-lOressure steam ; and to current steam, is confined steam.
It may be taken, as Dr. Fraser has said, that the use of superheated steam cannot be seriously supported. It has been definitely established that even on naked organisms its disinfectant value is much lower than that of saturated steam, and, as follows from the description of its behaviour in cooling, it is likewise very much slower in its penetration into objects. It is rsometimes forgotten that steam raised from saline solutions having a boiling point higher than that of water--the kind of steam contemplated in this article--is necessarily superheated. The reason is that it is the water in the solution and not the solution itself which is converted into steam. Accordingly the operation of boiling such solutions requires heat both for separating the water from the salt, and for converting the water into steam. The steam then becomes of the temperature to which the solution is raised by this amount of heat. It has
therefore received a larger amount of heat than is required to prevent it from condensing ; and until this excess of heat is removed, it cannot condense into water at the lower temperature necessary for condensation. In practical disinfection this only becomes a conclusive objection when the amount of superheat is such as to prevent the steam from being rapidly cooled to saturation. It hay, however, the disadvantage of increasing the time of penetration by an extent corresponding to the extent of the superheat ; though in disinfectors working at only a few degrees of superheat this may often be only a small matter. In the case, however, of disinfectors having a few degrees of super. heat, and working at or about the death-temperature of the organisms, it becomes a serious matter, the final few degrees of heat which are communicated from the superheated steam by the slow process of conduction being essential to the disinfection. The use of saline solutions accordingly entails the disadvantages and risk inseparable from superheated steam, and it depends upon various circumstances whether these objections, inevitably present to a greater or ~ess extent, are sufficiently grave to be fatal. The purpose for which their use has been suggested is the construction of cheap disinfectors for village and similar communities, where the expense of a dismfector working with steam under substantial pressure cannot be borne ; and the particular method of application which has been recommended for the purpose is that of current steam without pressure. For present practical purposes, accordingly, it is chiefly important to consider the efficiency of disinfectors working with steam in this state. It has recently been suggested that curi'ent steam without pressure penetrates objects more rapidly, and disinfects more efficiently, than steam under pressure. A statement to this effect occurs in Dr. Fraser's paper (PUBLIC HEALTH, October, i896 , P. 5), and the same statement has recently appeared elsewhere. The proposition amounts to thisuthat the hotter steam becomes, the less capable it is of heating objects in contact with it. This paradox was first stated by Koch in 188t. It was inconsistent with the experience of N~igeli and his pupils since I87o , and afterwards Koch's report was investigated by Buchner, Fitz, and others, who were unable to obtain the same results as Koch. The matter was ultimately cleared up by Heydenreich, in I884. He found that Koch's results could only be reproduced so long as a certain amount of air was mixed with the steam. Numerous independent instances of the inaccuracy of the statement were found. Globig killed dried spores by ten minutes' exposure to saturated steam under pressure at I2o°C., while they resisted five or six hours of current steam without pressure ; Gruber killed other spores with twenty minutes' exposure to saturated steam under pressure at x io°C., while they not only survived, but appe~ed to suffer no
DISINFECTION
BY STEAM
DERIVED
attenuation of any kind after exposure to current steam without pressure for two and a-half hours. Kitt, using symptomatic anthrax spores in dried muscle's~ found the organisms to survive six hours of current steam without pressure~ and to yield to twenty minutes of saturated steam under pressure at IIo°C. Quite recently Miquel rein,,estigated the whole question of the temperature proper ,for steam disinfection, his experiments being the most precise of any which I know on the subject of thermal death-points with steam ; and he found equally that 2o minutes at 1 Io?C. was indispensable for safety, and that no reasonable or practieable exposure, whether continuous or otherwise, to current s,eam without pressure was adequate. The proposition that current steam without pressure has a higher disinfecting power than ,aturated steam under pressure is, therefore, not only inaccurate, but has been known since i884 to express the exact contrary of the truth. It is precisely the same with the proposition that steam under pressure penetrates more slowly into porous objects than current steam without pressure. Many observers, in comparing different machines, found the exact contrary, notably Salomonsen and Levison. Budde worked with one machine at various pressures, and found that the higher the pressure the more the heat penetrated into objects. Pfuhl, using a machine of another construction at various pressures, obtained precisely the same result. Frosch and Clarenbach took the pressures up successively from one-fortieth to one-fifth of an atmosphere, and found that as the pressure increased so did the rate of penetration. In the whole collection of serious experiment on the subject which has been made in the last ten years, I know of no case in which current steam without pressure has given as good results~ either in point of penetration or of disinfection, as in like conditions has been given by steam under pressure. It is accordingly needless to occupy space in discussing the hypothesis by which Dr. Fraser thinks that the alleged inferiority of steam under pressure may be explained. Steam without pressure does not penetrate or disinfect so quickly as steam under pressure, and disinfectors working with it must be used, if at all, with proper regard to this fact. There is, however, a more serious objection to this method of using steam for disinfection. Not only the temperature obtained, but also the rate of disinfection varies with the velocity of the steam, i.e., with the way in which the fire is stoked. This was accidentally discovered by Esmarch, in Ig87, and thereafter verified by him in deliberate experiments. It has been confirmed wherever it has been examined in later years, down to the inquiry of the present year by Dr. Smith. Accordingly the temperature and the rate of disinfection in disinfectors working with current steam without pressure will vary with the energy of the attendaut, the nature of the coal,and similar circumstances
FROM
SALINE SOLUTIONS.
xox
entirely beyond the control of the responsible medical officer. I am confirmed in regarding this as a serious objection to the use of steam in this way, because, if anything is settled in regard to steam disinfection, it is that the operation shall as far as possible be made the subject of automatic control. This control can practically only be obtained by using saturated steam under some pressure capable of being recorded on a recording pressure-gauge. Where cheapness is absolutely indispensable this pressure is sometimes reduced to as little as one-twentieth of an atmosphere. The absence of some pressure by which the temperature of the steam can be known and controlled is, in the light of modern practice, a fatal obiection to the use of current steam without pressure. Apart from the control which is impossible without pressure, it is desirable to recognise that absolute disinfection cannot be assured without temperatures higher than can in practice be yielded by steam without pressure. It will be remembered that even where saline solutions are used, they cannot be allowed to give a temperature much higher than boiling point, for fear of increasing the risk due to the presence of superheat. In connection with the apparatus described by Dr. Fraser, it is stated that pathogenic organisms are infallibly destroyed by exposure to steam at 2~2 ° F. for five minutes. The statement in question is in t~o senses inaccurate. It is contradicted directly by facts that are known ; and it makes an assertion about things that are not known. The organism of symptomatic anthrax has repeatedly been shown, as in the experiments of Kitt, quoted above, to resist many hours' exposure to 212 ° F. Grancher and LedouxLabard have boiled tuberculous matter for one hour, and a second portion for three hours; in each case finding that the infection retained its virulence, the test-animals dying at lengths of time correspondin~ with the extent to which the matter had been boiled. I could multiply instances indefinitely, which directly contradict the proposition which I have quoted. It is ~aid, sometimes, that these are not the diseases against which we disinfect, and that if they were~ their organisms have been destroyed by lesser exposures. If, unfortunately, it be true that disinfection after and during tuberculosis is not yet usual in this country, as it is in America and elsewhere, it is to be hoped that this reproach may not continue for long ; and it does not alter the fact that some British authorities already practise it. That organisms perish at variable temperatures depending on all sorts of partly-known circumstances in their life-history is common knowledge, and the fact that some specimens of an organism have perished at a lower temperature does not alter the fact that other specimens have survived the higher temperature~ and may at any time do so again, But the proposition is al.~o inaccurate through the fact that o~ some infectiousdiseases,as small-pox and
tO2
D I S I N F E C T I O N BY STEAM D E R I V E D FROM SALINE SOLUTIONS.
seadet fever, the existing organism is not yet demonstrated; and that no "infallible" knowledge, and no knowledge at all of which account can be taken scientifically, exists as to the resistance of these unknown organisms to disinfection by steam. It has been suggested that they would probably follow the analogy of organisms such as those of typhoid fever and diphtheria, and perish below too ° C. It is equally conceivable that they may take the course of symptomatic anthrax, tuberculosis, and other organisms pathogenic and otherwise, and require much higher temperatures. Analogy, indeed, for what it may be worth, is rather in favour of the latter hypothesis. The circumstance pointed out in last month's _PUBLIC HEALTH,that the symptomatic anthrax organism may be preserved alive for at least ten years without loss of virulence, is singularly like the capacity of scarlet fever infection to persist for many years, and suggests the old native habit in India of successfully inoculating with the same piece of small-pox scab for an apparently indefinite time. A considerable responsibility is therefore undertaken by those persons who, in the face of these facts, use steam at or about ioo ° C., when they can procure the use of steam under adequate pressure. Nevertheless, where sufficient funds cannot be obtained, it is unquestionably better to use steam under very slight pressure than hot-air or sulphur chambers. I have set out the objections which exist to the use of current steam at atmospheric pressure. When this steam is derived from saline solutions, it is complicated by the disadvantages due to the presence of superheat. There are, however, other difficulties. Boilers in which steam is formed are liable to "prime," that is, to allow drops of water to be carried over by the steam. This phenomenon is usually most pronounced when the water contains impurities. I f this occurred in the use of saline solutions for disinfection, two consequences would follow. In the first place the strength of the solution, which no doubt would always be regulated by the admission of water up to a constant level, would vary, and with it the temperature of the steam. In the presence of the inevitable variations due to steam velocity, this would not be a matter of much importance in using current steam without pressure. But some of this liquid would naturally be absorbed by the objects under disinfection. This would not sensibly increase their weight after drying at the t i m e ; b u t with any deliquescent salt, such as calcium chloride, it would on exposure to an atmosphere not rigidly dry, serve to make ihe objects damp and to keep them so, unless the salt was washed out of them, a process which with many objects is practically impossible. I f there is any evidence to show that this priming, which would certainly be expected on generalgrounds, does not occur, I must say that I have not seen it. The same remark applies to the last objection which I
need mention to the use of saline solutions, that o n e would expect them after being used for some time, particularly when the use was discontinuous, to cause scale and ultimate corrosion of the boiler. I can therefore see no inducement, and can see considerable objection, to the employment of saline solutions for steam-raising in disinfection, and especially to the use of current steam without pressure derived from them. The matter does not, however, rest solely on the general considerations which I have set out. The use of saline solutions, suggested by Koch, in i88I, was actually carried out some two or three years later by Professor Dobroslavin, and a little afterwards by Dr. Emme. Dobroslavin's arrangement, the well-known ltu~e selhydriCue, consisted of a disinfecting chamber surrounded by a closed jacket. The solution was contained in the lower part of the space between the chamber and the jacket, and the steam, formed in the upper part of the same space, was conducted down in pipes through the hot solution, and thence led up into the disinfecting chamber. This arrangement, as will be seen by reference to Dr. Fraser's paper, is substantially the same as that which was recentlymI need not say quite independently-invented by Dr. Thresh ; and it certainly appears to give the steam every chance of doing its best. Disinfectors were made on this design, and used for some years. The net upshot was stated by Dobroslavin himself at the Congress of Vienna. He had found it necessary to abandon altogether the use of saline solutions, and had been able to do better with the disinfector by the use of ordinary water. In conclusion, I desire to point out that the considerations which I have discussed do not affect one or several disinfectors, but all steam disinfectors. If saline solutions were advantageous, they could be used by every authority possessing existing disinfectors. Every maker of such appliances could either adopt Dobroslavin's arrangement as it stands, or could modify it so as to retain any features in his existing appliances which he considered advantageous, or to provide such pressure as he might be advised was desirable. Contrariwise, any arrangement which was good for use with steam derived from saline solutions would serve with equal advantage for use with ordinary steam. I refer to the general nature of the discussion, because some people in this country have apparently a difficulty in realising that the discussion of the general principles involved in the construction of sanitary appliances is not necessarily equivalent to a recommendation of one or other machine. Such discussions, as distinguished from the bare recital of advantages attributed on the basis of sporadic experiment to individual appliances, have for many years been constantly going on abroad; and, in particular, they have largely contributed to form the data on which the construction and use of steam disinfectors should be based.
SERUM-DIAGNOSIS OF T Y P H O I D FEVER. SERUM-DIAGNOSIS OF T Y P H O I D FEVER. THE Board of Health of Quebec have taken an important step in regard to the diagnosis of typhoid fever, as wilt be seen from the circular, the substance of which we append. The practical result of this method of diagnosis will be watched with great interest ; and it need hardly be said that if the method of serum-diagnosis here set forth affords a means of ready and early diagnosis, it will furnish a substantial addition to the armament of preventive medicine : " T h e Board of Health of the Province of Quebec desires to call the attention of the medical profession and sanitary authorities of this Province to the fact that bacteriological methods seem hkely to afford a rapid and satisfactory method of diagnosis in typhoid fever, which will compare not unfavourably in point of efficiency with the methods now so widely employed for the diagnosis of tuberculosis and diphtheria. " I t has been shown by Pfeiffer of Berlin and Widal of Paris, that the serum obtained from the blood of a typhoid fever patient is capable of so acting upon pure bouillon cultures of typhoid bacilli mixed with it as to abolish the active motion so characteristic of that organism in fluid culture media, and cause an agglutination of the individual bacilli into large groups or clumps. This change is easily recognizable under the microscope--or in culture tubes--and usually occurs within a few minutes. "With serum from the blood of healthy persons or those suffering from febrile diseases other than typhoid, the motion of the bacilli is not arrested, but continues indefinitely when mixed with the typhoid culture. " T h e method as originally introduced by Pfeiffer involved somewhat difficult and complicated procedure for obtaining pure and sterile serum, but the process has recently been much simplified by Widal, who found that a few drops of blood collected in a sterilized glass tube, suffices for the test. c, Widal and Sicard state that the serum and blood, when dried, retain their power of producing this effect, though they do not record any practical application of this circumstance. " I t has been since shown by Dr. Wyatt Johnston, bacteriologist of this Board, that the fluid obtained by moistening with water a dried blood-drop gives the reaction in a prompt and satisfactory manner, even after it has been dried for several days. This modification of the process makes it more suitable for a system of free public laboratory diagnosis, similar to that in the case of diphtheria, as a drop of dried blood can be more readily sent to a laboratory and examined there. The bacteriolo gist of the Board was able to diagnose correctly by means of dried blood drops sent by mail from Montreal to Buffalo, N.Y., during the meeting of the American Public Health Association, in September, 1896 , those which were from typhoid
io 3
cases and those which were not, using no other means than the method described above. "As the subject is a new one, the Board does not feel in a position to state exactly what degree of accuracy will be obtained from this method, when used for the routine diagnosis of typhoid fever on a large scale, but in order to test the 2Oractt'calutility of the method, hereby offers to examine and report (gratis) upon any samples of blood collected by physicians of this Province, as directed in the instructions given with the outfits. A report will be sent by 2 p.m. upon the day following that upon which the sample is received, and will be communicated by telephone when the number is given. " T h e Board wishes to obtain data upon the following points, and earnestly requests the medical profession to aid them by furnishing any information bearing upon them :-" i. The proportion of cases in which a correct diagnosis can be made by the serum test, and the relative efficiency of the method of employing dried samples. "2. The earliest period in typhoid fever at which it can be expected to give indications. "3. The length of time for which it persists after convalescence. "4. The existence of any relation between the intensity of reaction with the test and the course of the disease. "5. The study ofthe nature of the obscure febrile conditions, clinically termed gastric fever, continued fever, abortive typhoid bilious fever~ typho-malarial fever, etc., about which our present knowledge is very meagre and unsatisfactory. " I t is hoped that those who take advantage of the offer now made by the Board will do all in their power to aid this inquiry by not only carefully filling up the blanks sent with the samples, but by afterwards giving information, when possible, as to whether the subsequent progress of the case confirmed the result of the serum test or not, and also by providing, when possible, temperature charts, etc., for study by the officials of the Board. " T h e Board is especially desirous of hearing promptly of and re-examining any genuine typhoid cases in which the method is not successful. In case of negative results, it is desired that the second time, an additional sample should also be sent, consisting of a few drops of blood collected in one of the glass tubes, which will be furnished on special application at the dep6ts. "With reference to the effect of drying the samples: while this may lessen slightly the delicacy of the reaction, it has the practical advantage of obviating, a serious source of error, namely, the contamination of the sample and the subsequent growth of putrefactive bacteria. This is of special importance in the case of samples having to be sent for long distances. "With regard to the significance of negativeresults, we may quote the following statement by Widal :
~o4
HEALTHY
,t, A negative result obtained with the serum of a case of suspected typhoid affords a presumption against the diagnosis of typhoid fever, but this is only a probability, especially if the examination has been made in the first few days of the disease. The examination should then be repeated during the next few days. The presumption that a case in which a negative result has been obtained is not typhoid, becomes correspondingly stronger as the stage of the disease becomes more advanced.'" HEALTHY MILK. DR. NIvE~, Medical Officer of Health of the City of Manchester, delivered a Lecture on the 9th ult. on " How a City may be Supplied with Good Milk," under the auspices of the Ancoats Healthy Homes Society. Dr. Niven said a vast number of children were swept away every year by diarrhoea, and the most searching enquiry showed that these deaths were directly caused by the milk on which the children were fed. This was often the fault of the mother by not taking the precaution to boil the milk, but it would not avail to boil the milk unless it arrived of sufficiently good quality. They could kill the living matter in the milk, but could not by boiling deprive it of its poisonous properties if it had become poisoned. Those injurious properties the milk too often acquired as soon as it came from the cow. Cows in a very large number of instances were infected with tubercular disease. In a certain proportion of cows, and practically in all when the udder had become tuberculou% the milk became infected, and was capable of giving children consumption of the bowels. Generally speaking, about twenty per cent. of the cows in this country were affected with this disease. Every now and then they also found widespread and disastrous epidemics of typhoid fever, scarlet fever, and diphtheria attributed to and clearly proved to have come from milk which had become infected, and they ought seriously to consider where it was a necessary thing for these evil consequences to accrue from the use of milk. About two years ago, Dr. Niven said, his attention was called to a pamphlet published by Mr. Stuart Macgregor, the British Vice-Consul in the Danish Capital, describing the system whereby they could have milk fragrant, pure, and clean. H e was sure every one would wRh that such milk should be brought into this community. I f milk were drawn from the cow on a summer day, and exposed a short time, a vast number of microorganisms developed, and caused changes in it which led to the production of elements that were poisonous to the human system. H e did not mean to say that all the milk used contained poisonous material, but that the milk used in summer was liable to contain such material. In August last, when he journeyed through Denmarl~ to Copenhagen, he found that the fields consisted
MILK. chiefly of red clover, and in these the cows grazed, and they were milked in the fields. H e went through one of the factories to which the milk was taken in cans--the employgs were compelled to put on clean cotton outer clothing as they came in to work--the milk was brought to the factory from the farms in railway trucks, and the cans were surrounded by ice, and the cows were periodically examined by the veterinary surgeons appointed by the company. They had one special quality of milk for the feeding of children, which was called "children's milk." For the supply of this they selected the best cows. The milk was tested by an expert, and if any of it was found to be in the sligh'est degree disagreeable, it was rejected. The cows were allowed no brewers' grains or turnips, but they were allowed carrots and beetroot. This special feeding was the result of careful experiment and scientific knowledge, and it was worthy of note that the chief food here was distinctly and absolutely excluded there. From the mqment of the milk leaving the cow, it was kept in a very low temperature, and as the cans or bottles left the factory for the consumer they were surrounded with ice. The company received the milk from fifty-seven large farms, each farm having from 5o to 20o cows. The total number of cows supplying the company last ~ear was 5,024, and the amount of milk supplied to the public in i894 was two million gallons. The farms he visited were beautifully clean, the floor was of concrete, and the cows were invariably littered with clean straw. The price in Denmark was ts. per gallon for the best milk, and he thought every one would agree, if they could get milk from English dairies protected in this manner, at a reasonable price, they would be conferring a great boon on the community, and he did not see any reason why it should not be done. S T E A M I N G IN C O T T O N W E A V I N G SHEDS
•
BY
EDWARD
SEROEANT, M.R.C.S., L.R.C.P., L.S.S.C., M.O.H. Lancashire.
THE agitation which has recently arisen against steam in certain districts of this countyj induced me to visit several weaving sheds in the Urban districts of Hurst and Padiham: and facilities have also been kindly extended to me for an examination of the conditions affecting weavers in the county boroughs of Blackburn and Preston. From personal knowledge of weaving sheds, extending over many years, I feel justified in saying that the working of the Cotton Cloth Factories Act, x889, has been productive of much good, and with few exceptions the limits of humidity allowed by the Act are faithfully adhered to. In the manufacture of heavily-sized cloth a high state of humidity seems to be necessary, and at the • From Annual Report, for I895, to the Lancashire County Council.