Part 7
That disease germs may be distributed with the vegetables grown on municipal sewage farms is not a mere whim or fancy of the faddist, but is a very real danger, and must be regarded as a menace to the health of all who consume such articles as lettuces, radishes, celery, and other vegetables which are not first cooked before being placed on the table.
This forcibly suggests the desirability of all expectorations from consumptive patients being thoroughly disinfected, or, in other words, deprived of their virulence before being admitted to sewage.
The importance of such precautions being taken is borne out by the examinations of the clear effluent derived from the treatment of the sewage of a consumptive hospital which revealed the presence of virulent tubercle bacilli, whilst they were also discovered in the bottom of a ditch conducting the effluent away.
Such facts as these deserve the earnest attention of all public authorities, and it is to be hoped that the overwhelming evidence which is now available regarding the distribution and Spartan character of the tubercle bacillus will lead to serious efforts being made to bestow upon it that measure of consideration which in the case of recognised zymotic diseases leads to the enactment of rules and regulations for the restriction at least of the fateful activities of these malignant foes of mankind.
Before leaving the subject of bacteria in relation to water, it will be interesting to glance at what is known regarding the attitude taken up by these minute forms of life towards that large and ever-increasing class of waters vaguely grouped together under the synonym of mineral waters. The fortunes made in manufacturing artificially aërated waters and the mine of wealth contained in a new mineral spring are sufficient evidence of the popularity enjoyed by this description of beverage. The beer and spirit statistics of the country and their contributions to the national revenue do not, however, permit us to indulge in the belief that this large consumption of harmless drinks is due to their displacing the use of intoxicants--the increasing sale of non-alcoholic beverages cannot in fact be taken as an index of the growing sobriety of a nation; far more must the greater demand be attributed to the improvements in manufacture which have cheapened production and placed what was formerly an article of luxury almost prohibitive in price, and hence reserved for the few, within comparatively easy reach of the many. Perhaps also an increased sale may be assisted by a prevailing impression that by substituting carbonated for ordinary potable water, the risk of contracting zymotic disease is, if not altogether removed, at any rate very materially diminished.
It will be therefore instructive to see how far this assumption is justified by actual facts.
The first fact to be recognised is that the number of bacteria present may and does fluctuate between such wide limits as is represented by as few as three, and as many as 100,000 being found in about twenty drops of artificially aërated waters. Seltzer water, manufactured from well water, was found by Sohnke to contain numbers varying from 200 to 6,000, whilst when only distilled water was used, _i.e._ water previously deprived of all bacterial life, only from ten to thirty microbes were present. But an important and far too little recognised factor in the manufacture of aërated waters is the contamination which so frequently takes place subsequent to the initial purification of the water by sterilisation. In some instances this contamination is due to the storing of water before use in reservoirs, where an excellent opportunity is offered for microbial multiplication.
Merkel found water which originally only boasted of from four to five bacteria per cubic centimetre, subsequently, when ready for distribution as seltzer water, contained considerably over 3,000. In this case storage had been resorted to. Again, insufficient importance is attached to the efficient cleansing of the syphons on their return to the factory. The experiments made by Slater in this country and Abba in Italy have conclusively shown that the gaseous aëration of water exerts an inhibitory action on the growth of at least some varieties of water bacteria, for both these investigators found that in proportion as the amount of gas present was diminished by being allowed to escape, so was the multiplication of the bacteria present promoted and their numbers increased. Unsavoury as may be the idea of swallowing down myriads of even harmless microbes, yet the real significance of the whole question from a hygienic point of view lies in the evidence as to the fate of disease germs in aërated waters.
On this important matter there fortunately exists some precise and conclusive information in regard to the bacteria associated with two essentially water-borne diseases, _i.e._ typhoid fever and cholera. The investigations made to test the vitality of the anthrax bacillus are of significance as again emphasising the superior degree of vitality possessed by the spore over the bacillar form of this micro-organism, but the chances of this disease being disseminated by water are usually regarded as too remote to excite much interest in the fate of the _b. anthracis_ in seltzer water. It may, however, be mentioned that whereas the bacilli succumbed after being in the seltzer water from fifteen minutes to an hour, the spores were still living after one hundred and fifty-four days. Investigations on the vitality of cholera bacilli in aërated waters have been made by Hochstetter in Germany, by Slater in England, and by Abba in Italy, and these various authorities all agree that the lease of life of these micro-organisms is a very short one in ordinary unsterilised carbonated waters, and that they are in fact destroyed in from half an hour to three hours. As regards typhoid bacilli the case is different, for the same investigators found that in ordinary unsterilised aërated water these bacteria can live as long as eleven days. In seltzer water their vitality is not so marked, but even then it greatly exceeds that of the accommodating cholera microbes, extending to five days.
Thus supposing typhoid bacilli to be present in the water employed for the manufacture of aërated waters--and we cannot afford to disregard such a possibility--we have no guarantee that such waters will be safe for drinking purposes unless a considerable period has been allowed to elapse between their production and consumption.
It was considerations of this kind which led M. Duclaux, the accomplished director of the Paris Pasteur Institute, to write now some years ago: "Contentons-nous de conclure que l'usage de l'eau de seltz, recommandé en temps d'épidémie peut en effet être recommandable, surtout si on laisse vieillir l'eau quelques jours. On a chance d'y voir diminuer ou même périr les germes nuisibles."
On the whole, therefore, the scientific report on bacteria and artificially aërated waters may be regarded as a reassuring one. It is to be regretted, however, that in England we do not follow the example set by Italy, where the aërated water manufacturers are closely looked after by the State, and no factory may be opened unless a satisfactory guarantee can be given of the chemical and bacteriological purity of the water which is intended to be used, whilst the authorities must also be assured that the methods employed are satisfactory from a hygienic point of view. The sale of all aërated waters prepared from insanitary water-supplies is strictly prohibited by the State.
It will now be of interest to ascertain what is the result of the endeavours which have been made to explore the bacterial flora of those highly prized and largely circulated natural mineral waters, which abound in so many parts of the world and are practically the making of so many health resorts.
Perhaps the most exhaustive examinations of mineral water which have been so far made are those published by Dr. Eugenio Fazio, who studied the bacterial condition of some of the celebrated springs situated near Naples at Castellamare, Telese, Acetosella, and Muraglione, care being taken to select examples of different types of water, samples being collected from chalybeate, carbonated sulphur, and alkaline springs respectively.
All these various mineral waters were characterised by a remarkable paucity of bacteria; in the chalybeate and alkaline springs sometimes as few as two microbes only in a cubic centimetre were found, and the largest number recorded only amounted to forty-five. The satisfactory significance of such figures will be appreciated when we realise that they rival very closely the numbers which characterise the purest spring and the deepest well water, and which are usually regarded as the aristocracy among drinking-waters. Of special interest is Dr. Fazio's discovery that the variety of bacteria present in these waters is extremely restricted, as a rule only three, or at most four, different kinds of bacteria being detected.
This is also characteristic of the pure water derived from deep wells sunk into the chalk, usually but very few different kinds of bacteria being found amongst the limited number of their Lilliputian inhabitants, whilst in samples collected from rivers or other surface sources, especially those which have been polluted with sewage or similar refuse matters, the bacterial population is frequently as diverse as it is unwieldy.
From the exacting point of view of the uncompromising bacteriologist the most satisfactory waters in existence for drinking purposes should be those derived from sulphur springs. Dr. Fazio and other investigators have frequently found absolutely no bacteria whatever in these waters, and often only four in a cubic centimetre. When we remember the high temperature of so-called thermal sulphur waters, which in many cases reaches more than fifty degrees Centigrade, it is perhaps surprising that even four individuals can be found in a cubic centimetre capable of withstanding the nauseous atmosphere of sulphuretted hydrogen in addition to such hot environment. Perhaps in the bacterial community these hot sulphur springs provide that place of punishment which figured so largely in the imagination of the early Christian fathers; certain it is that in this bacterial hell, in the picturing of which so many of the old masters seem to have revelled, but very few individuals are to be found, and those which are there are almost entirely derived from one family.
In giving weight to the highly satisfactory results of these bacterial examinations in forming an estimate of the microbial quality of natural mineral waters, it must be borne in mind that these investigations were all made of the said waters in a state of nature straight from the source, and before they had undergone the barbarous ordeal of commercial manipulation such as the process of bottling.
We are all of us sufficiently acquainted with the first principles of germ life to realise how deftly and how directly any inattention to hygienic details is reflected in the larder or the store-room; and it requires but little stretch of the imagination to picture the bacterial armaments which would at once invade these peaceful waters on the first suggestion of relaxed vigilance, or removal of that rigid surveillance so essential for their protection and preservation.
MILK DANGERS AND REMEDIES
It may with justice be said that in no department of applied bacteriology is more activity apparent than in that which has for its object the building up of a scientific basis for dairy practice. Although this is undoubtedly true, yet, unfortunately, unlike its continental neighbours, the British public, with whom practically rests the control of our dairy industries, has hitherto held itself strangely aloof, evincing little or no sympathy in researches which, even if they fail to interest, should surely impress with a sense of the great hygienic importance attaching to them. But this apathy is not only to be deprecated in the interests of health, but also on economic grounds.
We have only to turn to the reports issued by the Board of Agriculture to realise what this characteristic British apathy has brought about in the dairy industry of this country. Thus in the year 1898 we are officially informed that we imported 359,425,136 pounds of butter, the little country of Denmark alone sending over to us 163,883,360 pounds! Our cheese imports reached the enormous total of 262,018,624 pounds, whilst 817,274 cwts. of condensed milk and 10,691 of milk and cream were supplied to us from without.
If we glance at the energy and enthusiasm displayed by other countries, and notably Denmark, in the prosecution and scientific development of the dairy industry, we shall not wonder at the high standard of excellence achieved, or at the readiness displayed by Great Britain to absorb their produce. Thus, whilst in England it may be questioned whether in a single dairy the artificial souring of cream by pure cultures of bacteria is carried out, in Denmark the use of so-called special bacterial butter-starters is rapidly gaining ground. Thus, whereas in 1888 at the Odense Exhibition not a single sample of butter was exhibited in which pure bacterial cultures had been employed, in 1894, 46·7 per cent. of the samples shown were thus produced, in 1896, 89·2 per cent., in 1897, 94·4 per cent., 1898, 95·9 per cent, and in 1899, _every sample_, and since this year nearly every dairy of importance in the country employs special bacterial butter-starters.
The Danes are enlightened and shrewd enough to realise that in order to retain their existing markets and acquire fresh ones, it is necessary to take advantage of every improvement in methods of manufacture which scientific research has placed at their disposal, and their reward is justly reaped in the prosperity of their dairy industry and the high reputation enjoyed by their produce. If we contrast the adaptability and elasticity of the continental mind in regard to new discoveries with the crude conservatism of the British manufacturer, then, indeed, is the success of our rivals and corresponding decline of our own prosperity most perfectly intelligible.
Again, we are informed that the recent visit to London of a deputation representing Russian agricultural interests is already bearing fruit, and contracts have been signed for the regular importation of large quantities of Russian dairy produce. The English market is already well supplied with Russian eggs, but an opening has now been found here for the disposal of Russian butter and cheese.
Finland, again, the total population of which is less than half that of London, exports to this country no less than 12 million marks' worth of butter annually.
As a writer recently put it: "Foreigners and colonists have captured our butter markets; if the consumption of milk sterilised in bottles becomes the fashion, they will likewise capture our milk markets." And this is no fanciful suggestion, for whilst the production of Pasteurised milk does not involve any considerable outlay in apparatus, its transport may be effected with the greatest ease. Indeed, frozen milk has been introduced into England from Norway and Sweden. It is first Pasteurised, then frozen in large wooden boxes, and shipped in the congealed condition, in which state it remains unchanged for a long period of time.
But it is undoubtedly with the public that the responsibility really rests, for as long as it does not care to create the demand for Pasteurised dairy products all the efforts of enlightened agricultural authorities in this country must inevitably end in failure.
On the Continent and in America dairy-bacteriology, as already pointed out, has made enormous strides, and has practically revolutionised the conduct of dairy work; and if we could but rouse ourselves from our lethargy we likewise should be able not only to boast of progress, but also to better hold our own ground in this important branch of agriculture; and one result would be that dairy troubles, which for so long have been accepted as more or less necessary evils, would yield here, as they have done elsewhere, to a more rigid attention to details, the significance of which scientific research has so successfully shown.
Some of the most easily preventable, but at the same time most aggressively assertive, dairy troubles are undoubtedly directly dependent upon the conduct of milking operations.
In the first place, the cow itself is only too frequently in an uncleanly condition, and as its coat offers exceptional facilities for the harbouring of dust and dirt, the danger of foreign particles falling into the milk is always present unless precautions are taken to negative, or at least minimise, all such chances of contamination.
Professor H. L. Russell, of the Wisconsin Agricultural Experiment Station, cites in his little volume on _Dairy Bacteriology_ an instructive experiment which brings home very forcibly the importance of such precautions. A cow pastured in a meadow was selected for the experiment, and the milking was done out of doors, so as to eliminate as far as possible any intrusion of disturbing foreign factors into the experiment, such as the access of microbes from the air in the milking-shed. The cow was first partially milked without any precautions whatever being taken, and during the process a small glass dish containing a layer of sterile nutrient gelatine was exposed for one minute beneath the animal's body, in close proximity to the milk-pail. The milking was then interrupted, and before being resumed the udder, flank, and legs of the animal were thoroughly cleansed with water; a second gelatine surface was then exposed in the same place and for the same length of time. The results of these two experiments are very instructive. When the cow was milked without any special precautions being taken, 3,250 bacteria were deposited per minute on an area equal to the surface of a ten-inch milk-pail; after, however, the animal had been cleansed, only 115 bacteria were deposited per minute on the same area.
Thus a large number of organisms can, by very simple precautions and very little extra trouble, be effectually prevented from obtaining access to milk. Even in the event of the milk being subsequently Pasteurised, clean milking is of very great importance; but still more imperative is it when it is destined for consumption in its raw, uncooked condition. If we consider how cows become covered with dirt and slime, that obstinately adhere to them when they wade through stagnant ponds and mud, and realise the chance thus afforded for malevolent microbes to exchange their unsavoury surroundings for so satisfactory and nourishing a material as milk, then indeed precautions of cleanliness, however troublesome, will not appear superfluous.
That a very real relationship does exist between the bacterial and dirt contents of milk has been clearly shown by actual investigation. A German scientist has made a special study of the subject, and has determined in a large number of milk samples the amount of foreign impurities present per litre, and the accompanying bacterial population per cubic centimetre.
The following results may be taken as typical of those obtained: in milk containing 36·8 milligrammes of dirt per quart as many as 12,897,600 bacteria were present per cubic centimetre; in cleaner samples, with 20·7 milligrammes of dirt per quart, the number of bacteria fell to 7,079,820; whilst in a still more satisfactory sample, containing 5·2 milligrammes of dirt per quart, there were 3,338,775 bacteria per cubic centimetre.
Such results indicate how important a factor is scrupulous cleanliness in milking operations in determining the initial purity of milk, for there is no doubt that bacterial impurities in milk are in the first instance, to a very great extent, controlled by the solid impurities present.
I do not know of any determinations which have been made of the actual amount of such solid impurities present in our public milk-supplies, but such estimations have been made in many of those belonging to large cities in Germany. Thus, Professor Renk found in a litre of milk supplied to Halle about 75 milligrammes, whilst in another sample as much as 0·362 grammes per litre were detected. In Berlin 10 milligrammes, and in Munich 9 milligrammes per litre, were found. Dr. Backhaus has estimated that the city of Berlin alone consumes daily with its milk no less than 300 cwt. of cow-dung. If we associate these amounts of solid impurities with their consequent bacterial impurities, then we shall obtain some idea of what the microbial population of these milk-supplies may amount to.
These impurities are almost wholly preventable, but, unfortunately, but little importance is apparently attached to their presence in milk as a rule by dairymen.
In a letter published in the _Sussex Daily News_ a correspondent and well-known authority on dairy matters sounds a timely note of warning to our dairy managers:--
"I happen to know," he writes, "for a fact that Americans who visited one of our Dairy Shows at Islington were so disgusted at the method--or rather lack of cleanly method--exhibited there as our ordinary way of milking cows, that these visitors stated that nothing would induce them to drink milk while in England. I mention this circumstance so as to bring home to the minds of English dairy-farmers who may read this letter how very backward we are in this country as compared with more studious and careful foreign competitors. It is insisted upon by our foreign teachers that our cow-stalls are too short and not roomy enough, and our cow-houses badly constructed; that we do not (1) groom our cows or (2) clean the teats, nor (3) sponge their udders, bellies, and sides before milking with clean, tepid water; (4) that the milkers do not tie up the cow's tail nor clean their own hands and persons, nor (5) cover their clothes with a clean, well-aired blouse during milking; that (6) they generally milk in a foul atmosphere (bacterially), tainted with the odour of dung, brewer's grains, or farmyard refuse. I am sorry to state that there is too much solid fact about the contentions which, based upon bacteriology, are given as causes of injury to quality.... Cleanliness is now a matter requiring the primary attention of English dairy-farmers. The study of bacteria proves that such inattention is greatly the cause of foreign butters beating ours."
It follows as a natural sequence that all the cans and vessels used for dairy purposes should be absolutely beyond suspicion of contamination. Professor Russell has shown by actual experiment that, even where the vessels are in good condition and fairly well cleaned, the milk has a very different bacterial population when collected in them and in vessels _sterilised by steam_.
Two covered cans were taken, one of which had been cleaned in the ordinary way, and the other sterilised by steam for half an hour. Previous to milking the animal was carefully cleaned, and special precautions were taken to avoid raising dust, whilst the first milk, always rife with bacteria, was rejected. Directly after milking bacterial gelatine-plates were respectively prepared from the milk in these two pails, with the following results: In one cubic centimetre of milk taken from the sterilised pail there were 165 bacteria; in that taken from the ordinary pail as many as 4,265 were found.