SOURED MILK IN HEALTH AND DISEASE
When people are ill the best thing they can do is to place themselves in the hands of the doctor, who will try to regulate their lives, including their diet, in accordance with the conditions which science suggests as the most likely to lead to their recovery.
It is not the aim of this book to teach persons who should be under medical treatment to doctor themselves; soured milk may or may not be beneficial in their case—that is for the medical man to say; and further, if it should be beneficial the doctor ought to have its preparation under his control. Slight differences in quality and purity may count for much in cases of acute disease, differences which might not matter to the person who requires no medical attention, and who consumes the article as a health-giving food. A considerable body of evidence is already on record as to the potency in certain cases of soured milk as a curative agent, and it seems to have taken its place in medicine as a recognised remedy.
There is a wide field of usefulness, however, outside of the strictly medical one. Professor Metchnikoff has collected many striking examples of individuals and peoples inhabiting different parts of the world, who thrive, and in many cases attain to a great age, and whose diet consists largely of soured milk. He has made a wide and general inquiry into the causes which tend to shorten life, and makes out a strong case in support of the view that in many cases this is the result of what is called auto-intoxication or self-poisoning. In man and in the mammalia generally, the colon or large intestine is very largely developed; this organ is not of much value in the digestion of food, and seems to be chiefly a receptacle for waste material; it is, as a rule, extremely rich in bacterial flora, which produce putrefactive changes in the waste material. As a result various poisonous principles are evolved, and these find their way into the blood, accompanied frequently, there is every reason to believe, by the injurious bacteria themselves. In this way many diseases and ailments are produced which shorten life. The inquiry then naturally turns to what is the best way of dealing with this state of matters. It is known that the bacteria referred to flourish best in alkaline or at least non-acid surroundings, and it is known that these conditions very frequently exist in the large intestine. Acids are the best antiseptics; they have been used from time immemorial as preservatives; pickles are preserved in vinegar or acetic acid, and when milk is allowed to sour under proper conditions, the germs of putrefaction are destroyed or their activity inhibited, and it keeps a considerable time. Doubtless, in hot countries, it was this property of lactic acid which first led to milk being artificially soured with a view to its preservation as an article of food. So powerful is lactic acid in this respect that it is a custom in some countries to preserve meat by placing it in soured milk.
How can acids be applied so as to control the bacterial flora of the large intestine? Not in the ordinary way, because, when administered through the mouth, they are used up long before they can penetrate to the colon. The brilliant idea occurred to Professor Metchnikoff, of administering acid-producing germs which might work their way through the digestive system, and, reaching the large intestine, produce the acid required. After much experimenting the bacillus of Massol, Bacillus bulgaricus, was adopted as the most suitable. The Bulgarian bacillus is an extremely vigorous one, multiplying with great rapidity, and persisting in conditions that would be inimical to other microbes. The growth and development of bacteria is interfered with by the products of their own activity; thus, ordinary lactic-acid-producing organisms die when a certain amount of lactic acid has been developed; the same fate overtakes the Bulgarian bacillus, but it survives longer and is able to produce as much as two and one half per cent. of lactic acid in milk before it ceases operations. It seemed therefore the most likely to be able to survive the journey through the digestive system. Experiments fully bore out this supposition, as no great difficulty was encountered in naturalising the Bulgarian bacillus in the large intestine, not only in milk cultures, but grown in solution of malt, bouillon, etc. It thrives in all kinds of sugar, and therefore can be administered in a variety of media, very beneficial results following in many cases. Direct tests showed a large reduction of the injurious intestinal flora when the Bulgarian bacillus had been naturalised in the colon, and the bacillus persisted long after it had ceased to be administered. Specialists who have taken up the subject report the cure of many ailments through the agency of soured milk, and it seems to have entered upon a lengthening career of medical usefulness.
The fact of so many old people being found in countries where soured milk is a staple of diet naturally raises the question as to whether its general use in other countries might not have a beneficial effect on health and longevity. Its usefulness as a remedial agent in certain diseases is already demonstrated; is there not a strong probability, amounting almost to a certainty, that its consumption by people in health would tend to ward off many ailments and prolong life? Of course there will be some for whom it is not suitable; there are people who cannot eat strawberries without discomfort, but no one thinks of prohibiting the general use of the fruit on that account. In the matter of diet the person in health, if he exercises ordinary care, may be left to find out for himself what suits him. The soured milk remedy is not a disagreeable one, as, when properly prepared, the article forms both a pleasant and refreshing article of diet. The question of getting the right article, however, is a very important one. Milk is a splendid rearing ground for many bacteria, some of which are very injurious; among these may be pathological germs, the seeds of tuberculosis, enteritis, etc. The danger with soured milk is, that in the process of culture we develop the best condition for the increase of these when they preponderate, or when, through the use of bad cultures, the lactic-acid-producing bacteria are absent, or present only in small numbers. By the thorough boiling of the milk, we get rid of all living bacteria and nearly all spores or germs, and by scrupulous cleanliness in the vessels used—scalding or even boiling them, and allowing them to dry naturally in an inverted position—we greatly diminish the probability of infection with fresh injurious germs from the atmosphere. All depends on the purity of the culture employed; this can now be obtained, prepared in the most careful manner, from wholesale chemists making a speciality of its manufacture.
As we have seen, even the Bulgarian bacillus is ultimately killed by the products of its own activity, and the natural corollary is, that the life of cultures cannot be a long one. Only those cultures should be bought which are labelled with the date to which they are guaranteed to maintain their efficiency. With fresh good milk, careful boiling, scalding, and cleanliness with regard to the containing vessels, and the means of maintaining the incubating temperature for ten or twelve hours, there is not the slightest difficulty in preparing perfectly reliable soured milk. There are simple tests which will sufficiently guide the experimenter; the soured milk should not be too acid to the taste, and it has a flavour of its own by which its quality can be recognised. The litmus test-papers mentioned in the chapter on the chemistry of milk are very useful; both the red and the blue papers should be obtained and used first of all in testing the quality of the fresh milk. After incubation the soured milk should turn the blue paper decidedly red; if this does not occur, test it with the red paper; if the latter turns blue it is proof that the wrong fermentation has taken place—that putrefactive germs have gained the upper hand. The most probable explanation is, that the culture is bad, the Bulgarian bacillus is not present, or if so, only in small numbers. With these simple tests, combined with proper care, one cannot go far wrong. The Eastern nations who prepare soured milk in various forms do not exercise the care we have predicated, but they seem to make the article of fairly constant and good quality. It has been suggested in explanation that, as the ordinary flora differs in different countries, the bacterial flora varies in a similar manner, and that in these Eastern countries injurious bacteria are not so prevalent in the atmosphere as they are with us.
It is also said that the flavour of the soured milk prepared in Bulgaria is quite different from that prepared in Paris, London, or New York; one reason probably is that the "maya" or ferment used in Bulgaria contains several other organisms besides the Bulgarian bacillus, which raises the question whether a pure culture of one bacillus is the best to use.
Professor Metchnikoff found that this bacillus alone had certain defects; it attacks fat and is apt to give a tallowy taste when cream is present in the milk. He therefore associated with it another lactic-acid-producing organism, and this combination is the basis of his culture called "lactobacilline." The presence of yeasts, which occur in the Eastern ferments, has been advocated by some; the yeast in association with the lactic organisms produces a small amount of alcohol. The question of the composition of the culture will have to be fought out by the experts, but meantime, if we go to the right source, we have good enough cultures to go on with.
A good deal can be said for the use of skimmed or separated milk instead of whole milk. Cream as a rule contains far more bacteria than the rest of the milk, and we therefore start from a surer foundation when it is removed; besides, the mechanical separator, now so largely used, removes slime and other impurities from the milk, and these also are hotbeds of bacteria.