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.
Another experiment illustrates perhaps even more strikingly the effect
of cleanly operations in milking upon the initial bacterial contents
of milk. The preliminary precautionary measures were carried out by an
ordinary workman, and are in no sense so refined as to be beyond the
reach of ordinary daily practice. "The milk was received in steamed
pails, the udder of the animal, before milking, was thoroughly carded,
and then moistened with water, so as to prevent dislodgment of dirt.
Care was taken that the barn air was free from dust, and in milking
the first few streams of milk were rejected. The milk from a cow
treated in this way contained 330 bacteria per cubic centimetre, while
that of the mixed herd, taken under the usual conditions, contained
15,500 in the same volume. The experiment was repeated under winter
conditions, at which time the mixed milk showed 7,600 bacteria per
cubic centimetre, while the carefully secured milk only had 210 in the
same volume. In each of these instances the milk secured with greater
care remained sweet over twenty-four hours longer than the ordinary
milk."
An organism which has exceptional opportunities for finding its way
into cows' milk is the _Bacillus coli communis_, normally present in
the fæces of all animals. This microbe is a very undesirable adjunct
to milk, and may greatly interfere with the souring process, by
multiplying extensively, and so producing a change in the milk which
renders it impossible for the particular souring bacteria to carry on
their work, resulting in their collapse and ultimate extinction. But
this is not the only injurious effect which these Coli bacilli can
produce in milk, for there is a growing conviction that their presence
is responsible for many intestinal disturbances with which young
children are specially troubled. Quite recently determinations of the
bacterial contents of cow-dung have been made, and it has been
ascertained that _a single gramme_,[6] freshly collected, of this
material may contain as many as 375,000,000 bacteria, of which the
majority were found to be the above undesirable organism, the _B. coli
communis_.
[6] One gramme = 15 grains.
Milk may also contain bacteria characterised by their remarkable
resistance to heat, which is due to their possessing what is known as
the hardy spore in addition to the ordinary rod form. The numbers in
which they are present in milk varies with different samples; but they
may be taken as a sort of index as to the care observed in milking,
for they are always present in great quantity in uncleanly-collected
milk. Careful studies have been made of this class of milk bacteria by
Professor Flügge and others, and it has been found that when added to
milk upon which puppies were subsequently fed the latter succumbed
under symptoms of violent diarrhoea.
The danger of even a few bacteria gaining access to milk is serious,
on account of the fabulous rapidity with which they multiply when they
find themselves in such congenial surroundings. Professor Freudenreich
has made very exhaustive investigations to show how milk microbes may
multiply in the time which elapses between milking and the receipt of
the milk by the consumer. The following example will convey some
notion of what bacterial propagation under these circumstances is
capable of.
The sample of milk in question was found to possess on reaching the
laboratory, two and a half hours after milking, a little over 9,000
bacteria in a cubic centimetre. The sample was divided into three
portions, which were kept at different temperatures, and after
definite intervals of time they were examined. The following table
shows at a glance the results obtained:--
NUMBER OF BACTERIA IN ABOUT TWENTY DROPS OF MILK.
+-----------------+---------------------------------------+
| | Temperature. |
| When Examined. +------------+-------------+------------+
| | 15° C. | 25° C. | 35° C. |
+-----------------+------------+-------------+------------+
| After 3 hours | 10,000 | 18,000 | 30,000 |
| After 6 hours | 25,000 | 172,000 | 12,000,000 |
| After 9 hours | 46,000 | 1,000,000 | 35,280,000 |
| After 24 hours | 5,700,000 | 577,500,000 | 50,000,000 |
+-----------------+------------+-------------+------------+