Chapter XIII: Part IV: Should We Try to Prolong Human Life? (2)

Soured milk, because of the lactic acid in it, can impede the putrefaction of meat. In certain countries, accordingly, meat is preserved in acid skimmed milk with the result that putrefaction is prevented. Lactic acid fermentation is equally important in the food supply of cattle. It is the chief agent that, in the process of preserving vegetation in silos, hinders putrefaction. Finally, the same fermentation serves in distilleries to preserve the must from which alcohol is prepared.

This short review is in itself enough to show the great importance of lactic fermentation as a means of stopping putrefaction and butyric fermentation, both of which hinder the preservation of organic substances and are capable of exciting disturbances in the organism.

As lactic fermentation serves so well to arrest putrefaction in general, why should it not be used for the same purpose within the digestive tube?

It is a matter of common knowledge that putrefaction and butyric fermentation are arrested in the presence of sugar. Whereas meat preserved without special care soon putrefies, milk in exactly the same conditions does not putrefy, but becomes sour, the reason being that meat is poor in sugar whereas milk contains a good deal of it. However, the scientific explanation of this fundamental fact is difficult. It has been shown conclusively that sugar itself cannot prevent putrefaction. Milk, for instance, however rich in sugar it may be, readily putrefies in certain conditions. Sugar preserves organic matter from putrefaction only because it can readily undergo lactic fermentation, and this fermentation is the work of the microbes described fifty years ago by Pasteur. That great discovery proved the part played by microbes in fermentation and founded bacteriology, a science equally rich in theory and in practice.

I need not pause to develop the theme that the anti-putrescent action of the lactic fermentation depends on the production of lactic acid by microbes, because I have explained the matter at length in the tenth chapter of the “Nature of Man.” If the lactic acid be neutralised, the organic matter soon putrefies, notwithstanding the presence of the lactic microbes. The most important point is as to whether lactic fermentation really arrests intestinal putrefaction. Several sets of observations have been made upon this matter. Dr. Herter,[132] of New York, injected directly into the small intestine of a number of dogs quantities of different microbes. To test the action of these on intestinal putrefaction, he investigated the sulpho-conjugate ethers in the urine, as he believed, in accordance with current and well justified opinion, that these substances are the best proofs of the existence of putrefaction. He found that whilst the introduction of quantities of _Bacillus coli_ or _Bacillus proteus_ increased the intestinal putrefaction, lactic bacilli notably lessened it. Herter found a notable diminution of sulpho-conjugate ethers in the urine of dogs which had been treated with the lactic microbes.

The experiments which Dr. M. Cohendy[133] performed upon himself during a period of nearly six months are still more interesting.

When Dr. Cohendy had proved that much intestinal putrefaction occurred during a period of 25 days, in which he lived on an ordinary mixed diet, he began to take pure cultures of lactic bacillus, taken from yahourth. In a period of 74 days, he took quantities varying from 280 to 350 grams of the culture.

Analysis of the urine during the progress of the experiment showed that intestinal putrefaction had notably decreased whilst the lactic bacilli were being taken, and that the diminution persisted seven weeks after the taking of the bacilli ceased. Dr. Cohendy gives it as the direct result of his experiment that the introduction of lactic ferment into the intestine definitely arrests putrefaction. He obtained this result on a diet consisting of 400 grams of soup, 150 of meat, 700 of grain-food, 400 of green vegetables, 300 of fruits and dessert and a litre of water. He came to the conclusion that the elimination of meat from the diet was unnecessary, as the particular kind of lactic ferment he employed was extremely active in inhibiting the proteolytic ferments.

Later experiments made by Dr. Cohendy showed that the lactic bacillus became so acclimatised in the human intestine that it was to be found there several weeks after it had been swallowed.

Dr. Pochon, assistant to Professor Combe[134] at Lausanne, has repeated on himself the experiments of Cohendy. He took for several weeks milk curdled with pure cultures of lactic acid microbes and obtained “results that were quite definite as to intestinal putrefaction.” Analysis of his urine showed that there was a marked diminution of indol and phenol, substances which are certain indexes of intestinal putrefaction.

In addition to such observations on lactic bacilli there is a good deal of knowledge as to the effect of lactic acid taken in bulk. The result of the various observations[135] shows that the acid lessens intestinal putrefaction and lowers the quantity of sulpho-conjugate ethers in the urine. This fact explains why favourable results follow the use of lactic acid in many intestinal diseases such as infantile diarrhœa, tuberculous enteritis and even Asiatic cholera. The addition of this remedy to practical therapeutics is due chiefly to Professor Hayem. It is employed not only in the treatment of diseases of the digestive system (dyspepsia, enteritis and colitis), but is indicated also in diabetes and is used locally in tuberculous ulcerations of the larynx. As quantities up to twelve grams can be given by the mouth daily, it is plain that the system is tolerant of this acid. It is either oxidised in the tissues or excreted with the urine. In the case of a diabetic woman who had taken 80 grams of lactic acid in four days, Nencki and Sieber[136] found no traces of it in the urine. On the other hand, Stadelmann[137] found a notable quantity of the acid in another diabetic patient who had been taking over four grams daily.

The general interpretation of the benefits gained from the use of lactic acid ferments is that they depend solely on the action of the lactic acid which they produce in preventing the multiplication of the microbes which cause putrefaction. Recent investigations made by Dr. Bélonowsky, at the Pasteur Institute, show that a lactic ferment isolated from yahourth and described as the Bulgarian bacillus owes its antiseptic powers not only to lactic acid but to another substance which it secretes. Dr. Bélonowsky has studied the effects of this bacillus upon mice, by adding to their previously sterilised food quantities of this lactic microbe. As control experiments he fed other mice on food to which lactic acid had been added in quantities corresponding to the quantity produced by the Bulgarian bacillus, or which had been mixed with other kinds of bacilli. Another set of mice were given normal food without the addition of either microbes or lactic acid.

Out of these groups of mice, those which had been given the Bulgarian bacillus thrived best and had most progeny. Their droppings showed fewest microbes, particularly microbes of putrefaction.

The next stage in Dr. Bélonowsky’s experiments was to feed mice not with living quantities of the Bulgarian bacillus, but with cultures which had been sterilised by heat (120°-140° Fahr.). These mice lived as well as those to which living cultures had been supplied, and notably better than those supplied with pure lactic acid. It is evident therefore that there is some other product of this bacillus which favours life by preventing intestinal putrefaction.

Dr. Bélonowsky showed, moreover, that the Bulgarian bacillus cures a special intestinal disease known as mouse typhus.

The experiments which I have described show that intestinal putrefaction is to be combated not by lactic acid itself, but by the introduction into the organism of cultures of the lactic bacilli. The latter become acclimatised in the human digestive tube as they find there the sugary material required for their subsistence, and by producing disinfecting bodies benefit the organism which supports them.

From time immemorial human beings have absorbed quantities of lactic microbes by consuming in the uncooked condition substances such as soured milk, kephir, sauerkraut, or salted cucumbers which have undergone lactic fermentation. By these means they have unknowingly lessened the evil consequences of intestinal putrefaction. In the Bible soured milk is frequently spoken of. When Abraham entertained the three angels he set before them soured milk and sweet milk and the calf which he had dressed (Genesis xviii. 8). In his fifth book, Moses enumerates amongst the food which Jehovah had given his people to eat “Soured milk of kine and goat’s milk, with fat of lambs and rams of the breed of Bashan, and goats with the fat of kidneys” (Deut. xxxii. 14).[138]

A food known as “Leben raib,” which is a soured milk, prepared from the milk of buffaloes, kine or goats, has been used in Egypt from the remotest antiquity. A similar preparation known as “yahourth” is familiar to the populations of the Balkan Peninsula. The natives of Algiers make a kind of “leben” not identical with the Egyptian form.

Soured milk is consumed in great quantities in Russia in two forms, “prostokwacha,” which is raw milk spontaneously coagulated and soured, and “varenetz,” which is boiled milk soured with a yeast.

The chief food of many natives of tropical Africa consists of soured milk. The staple diet of the Mpeseni is “a curdled milk, almost solidified.” “Meat is eaten only on ceremonial occasions.” According to Foà, a tribe of the Nyassa-Tanganyika plateau, like the Zulus, take milk only in the form of a raw cheese mixed with salt and pepper.

Dr. Lima of Mossamedes, in West Africa, has told me that the natives of many regions south of Angola live almost entirely on milk. They employ the cream as an ointment for the skin, whilst the milk, soured and curdled, is their staple food. M. Nogueira reported the same circumstances nearly fifty years ago after his journey in the province of Angola.

Just as cheeses vary in different countries, so curdled milk varies slightly according to the nature of the flora of microbes. Taking all the soured milks that are produced by natural processes, it may be said that the greater number of them contain not only microbes that produce lactic acid, but also yeasts that cause alcoholic fermentations. Kephir, which is prepared from the milk of kine, and koumiss, which is a product of mares’ milk, are notably alcoholic. Koumiss is the well-known national beverage of the Kirghises, Tartars and Kulmucks, nomads of Asiatic Russia who are famous horse breeders, whilst kephir is the native drink of the mountaineers of the Caucasus, the Ossetes, and some other tribes.

It has been supposed that the chief merit of kephir was that it was more easy to digest than milk, as some of its casein is dissolved in the process of fermentation. Kephir, in fact, was supposed to be partly digested milk. This view has not been confirmed. Professor Hayem thinks that the good effects of kephir are due to the presence of lactic acid which replaces the acid of the stomach and has an antiseptic effect. The experiments of M. Rovighi, which I spoke of in _The Nature of Man_, have confirmed the latter fact, which now may be taken as certain. The action of kephir in preventing intestinal putrefaction depends on the lactic acid bacilli which it contains.

Kephir, although in some cases certainly beneficial, cannot be recommended for the prolonged use necessary if intestinal putrefaction is to be overcome. It is produced by combined lactic and alcoholic fermentations, and as it contains up to one per cent. of alcohol, its use as a food for years would involve the absorption of considerable quantities of alcohol. The yeasts which produce it can be acclimatised in the human digestive tract, in which, however, they are harmful, as they are favourable to the germs of infectious diseases such as the bacillus of typhoid fever, and the vibrio of Asiatic cholera.

Kephir has also the disadvantage that its flora varies considerably and is not well known. There has been little success in producing it by pure cultures as would be necessary were it to be brought into general use. When it is prepared from a dried remnant there is the risk of stray microbes being included, and these may bring about pernicious fermentations. Professor Hayem prohibits its use in the case of persons in whom food is retained for long in the stomach. “When it is retained in the stomach, kephir goes on fermenting, and there are developed in the contents butyric and acetic acids which aggravate the digestive disturbances.”[139]

As it is the lactic and not the alcoholic fermentation on which the valuable properties of kephir depend, it is correct to replace it by soured milk that contains either no alcohol or merely the smallest traces of it.

The fact that so many races make soured milk and use it copiously is an excellent testimony to its usefulness. M. Nogueira has written to me to say how much he was astonished, on revisiting after a long period of absence the district of Mossamedes, to find the natives so well preserved and displaying so few traces of senility. Dr. Lima has stated that amongst the natives of the region south of Angola “many individuals of extraordinary longevity are to be found.” Although they are thin and withered, these old people are very active and can make long journeys.

Mr. Wales, a lawyer at Binghampton, U.S.A., has been so good as to make me acquainted with some extremely interesting facts taken from a work by James Riley which is now a bibliographical rarity.[140] In the narrative of a shipwreck of the vessel on which he made a voyage in 1815, James Riley states that the wandering Arabs of the desert live almost wholly on the milk of camels, fresh or soured.

On this diet they enjoy excellent health, display great vigour and reach advanced ages. Riley estimated that some of the old men must have lived for two to three hundred years. No doubt these figures are much too high, but it is probable that the Arabs Riley encountered lived really unusually long.

Mr. Wales has examined Riley’s work critically, and is of the opinion that that author was a well-informed, sagacious and conscientious observer.

M. Grigoroff, a Bulgarian student at Geneva, has been surprised by the number of centenarians to be found in Bulgaria, a region in which yahourth, a soured milk, is the stable food. Some of the centenarians, described by M. Chemin in his memoir, lived chiefly on a milk diet. Marie Priou, for example, who died in the Haute-Garonne in 1838 at the age of 158 years, had lived for the last ten years of her life entirely on cheese and goat’s milk (_op. cit._ p. 100). Ambroise Jantet, a labourer of Verdun, who died in 1751 at the age of 111 years, “ate nothing but unleavened bread and drank nothing but skimmed milk” (p. 133). Nicole Marc, who died aged 110 years, at the chateau of Colemberg (Pas-de-Calais), a hunch-back and cripple, “lived only on bread and milk-food. It was only towards the end of her life and after much persuasion that she took a little wine” (Chemin, p. 139).

I owe to the kindness of M. Simine, an engineer in the Caucasus, the following communication, taken from the newspaper _Tiflissky Listok_, Oct. 8th, 1904. “In the village of Sba, in the district of Gori, there is an old Ossete woman, Thense Abalva, whose age is supposed to be about 180 years (?). This woman is still quite capable and looks after her household duties and sews. Although she is bent, she walks firmly enough. Thense has never taken alcoholic liquors. She rises early in the morning, and her chief food is barley bread and butter milk, taken after the churning of the cream. Butter milk is a liquid containing very many lactic microbes.

Mrs. Jenny Read, an American, has written to me that her father, eighty-four years old, “owes his health to the curdled milk which he has taken for the last 40 years.”

Curdled milk and the other products of milk to which I have referred are the work of the lactic microbes which produce lactic acid at the expense of milk sugar. As many different kinds of soured milk have been consumed on a vast scale and have proved to be useful, it might be supposed that any of them is suitable for regular consumption with the object of preventing intestinal putrefaction.

From the point of view of flavour I find that soured milk, prepared from raw milk, is much the more agreeable. However, when a food is to be selected for consumption during a long period of time, we must keep hygiene strictly in view. It is certain, therefore, that the Russian “prostokwacha,” as well as any other soured raw milk, must be rejected. Raw milk contains a large assortment of microbes, and frequently some of these are harmful. The bacillus of bovine tuberculosis, as well as other pernicious microbes, may be found in it. According to the investigations of Heim[141] the vibrios of Asiatic cholera, when placed in raw milk, survive even when the milk has become quite soured. In similar conditions the bacillus of typhoid fever remains alive for 35 days and dies only after it has been kept for 48 days in completely soured milk.

As raw milk nearly always contains traces of fæcal matter from the cow, it sometimes happens that pernicious microbes are introduced from that source, and remain alive notwithstanding the acid coagulation of the milk. The lactic microbes certainly prevent the multiplication of other microbes, as, for instance, those of putrefaction, but are incapable of destroying them. Moreover, raw milk often contains fungi (yeasts, torulas, and oïdia) the presence of which is favourable to the development of such pernicious microbes as the cholera vibrio and the bacillus of typhoid fever.

Prolonged consumption of raw milk increases the risk of introducing dangerous microbes into the organism, and this possibility drives me to recommend soured milk prepared after heating. Theoretically, it would be best to sterilise the milk completely so that all the contained microbes would be destroyed. This, however, requires heating the milk to a temperature of from 226° to 248° Fahr., by which it acquires an unpleasant flavour. On the other hand, the pasteurising of milk at a temperature of about 140° Fahr. is not sufficient to get rid entirely of the bacilli of tuberculosis and the spores of the butyric bacilli. We have, therefore, to fall back on a middle course, and be content with boiling the milk for several minutes. By so doing we certainly kill the tubercle bacilli and the spores of some of the butyric bacilli,[142] there being left only some butyric spores and the spores of _Bacillus subtilis_, to destroy which a much higher temperature is necessary.

As some kinds of soured milk, such as “varenetz,” “yahourth,” “leben,” etc., are prepared from boiled milk, it might be supposed that they fulfil the conditions necessary for prolonged use. A closer examination, however, makes us reject them.

Boiled milk, to make it undergo the lactic fermentation properly, must have added to it a prepared ferment. What is necessary is not merely rennet, as was formerly supposed, but a number of organised ferments, that is to say, microbes. In the preparation of these soured milks, a leaven is employed, one of the names of which is “Maya,” and which contains not only lactic microbes, but several others. MM. Rist and Khoury[143] have come to the conclusion that the Egyptian “leben” contained a flora composed of five species, three of which are bacteria and two yeasts. The bacteria produce lactic acid and the yeasts alcohol. Although the result is that “leben” is a nearly solid substance, whilst kephir is a liquid, the two are closely similar. In both cases we have to do with coincident lactic and alcoholic fermentations, and my remarks regarding kephir apply equally well to the Egyptian “leben.”

Through the agency of Prof. Massol of Geneva, I have obtained a specimen of the Bulgarian “yahourth.” Working with his pupil, M. Grigoroff, M. Massol[144] has isolated several microbes from this milk, amongst these being a very active lactic bacillus. The same soured milk has been studied in my laboratory by Drs. M. Cohendy[145] and Michelson. They found in it a very powerful lactic ferment, which has been named the Bulgarian bacillus. This was the microbe employed in the experiments of M. Bélonowsky, to which I have already referred. More recently, it has been carefully investigated from the chemical point of view by MM. G. Bertrand and Weisweiler[146] at the Pasteur Institute. It proved to be an extremely active producer of lactic acid, supplying 25 grammes per litre of milk. The other acids which this bacillus produces, such as succinic and acetic acids, are formed only in very small quantities (about 50 centigrams a litre). Formic acid is produced only in traces. On the other hand, the Bulgarian bacillus forms neither alcohol nor acetone, two frequent products of bacterial fermentation. The bacillus also differs from other lactic ferments inasmuch as it has no action on albuminoids (casein, etc.), nor on fats. All these qualities make the Bulgarian bacillus much the most useful of the microbes which can be acclimatised in the digestive tube for the purpose of arresting putrefactions and pernicious fermentations, such as the butyric fermentation.

As in all the known soured milks (yahourth, leben, prostokwacha, kephir, and koumiss) the lactic bacilli are associated with a rich flora in which pernicious microbes may be met (such as the red torula, a microbe which predisposes to cholera and typhoid fever, which I found in the leaven of yahourth, bought in Paris), it is necessary to work out a method by which good curdled milk can be produced with the aid of pure cultures of the lactic microbes.

It was the obvious course to begin with the Bulgarian bacillus, as that is known to be the best producer of lactic acid. It coagulates milk rapidly, giving it a strongly acid flavour, but it often also gives a disagreeable taste of tallow. It is true that after it has been kept for a long time in the laboratory in the form of pure cultures in sterilised milk, the bacillus loses to a large extent its power of saponifying fats, the taste of the curdled milk being then more agreeable. If necessary, therefore, soured milk prepared exclusively with the Bulgarian bacillus can be used. In practice, however, it is useful to associate with it another lactic microbe, known as the paralactic bacillus, as the latter, although producing less lactic acid than the Bulgarian bacillus, does not break up the fats and gives the curdled milk a very pleasant flavour.

As it is undesirable to absorb too much fatty matter, it is necessary to prepare curdled milk for regular use from skimmed milk. After the milk has been boiled and rapidly cooled, pure cultures of the lactic microbes are sown in it, in sufficient quantities to prevent the germination of spores already in the milk and not destroyed in the process of boiling. The fermentation lasts a number of hours, varying according to the temperature, and finally produces a sour curdled milk, pleasant to the taste and active in preventing intestinal putrefaction. This milk, taken daily in quantities of from 300 to 500 cubic centimetres, controls the action of the intestine, and stimulates the kidneys favourably.[147] It can therefore be recommended in many cases of disorder of the digestive apparatus, of the kidneys, and in several skin diseases.

The Bulgarian bacillus taken from yahourth or from soured milk, prepared from pure cultures of lactic microbes, can live in warm temperatures, and, as has been shown by Dr. Cohendy, is able to take its place in the intestinal flora of man.

Soured milk, prepared according to the receipt which I have given, has been analysed by M. Fouard, an assistant at the Pasteur Institute. When it was ready to be taken, M. Fouard found in it about 10 grammes of lactic acid per litre. Moreover, a large proportion (nearly 38 per cent.) of the casein had been rendered soluble during the fermentation, which shows that its albuminous matter is prepared for digestion much as in kephir. Of the phosphate of lime (which is the chief mineral substance of milk) 68 per cent. was rendered soluble during the fermentation. These facts all confirm the utility of the soured milk prepared from pure cultures of lactic bacteria.

Those persons who, from some reason or other, cannot take milk, may swallow the bacilli in a pure culture without milk. However, as the microbes need sugar to produce lactic acid, it is necessary to take with them a certain quantity of sweet food (jam, sweet-meats, and especially beetroot).

The Bulgarian bacillus produces lactic acid not only from milk sugar, but also from many other sugars, for instance, cane sugar, maltose, levulose and especially glucose.

Cultures of the bacillus can be made not only in milk, but in vegetable broths, or broths of animal peptone to which sugar has been added. The cultures can be taken in a dry form (powders or tabloids), or in the liquid in which the bacilli had themselves been developed.

A reader who has little knowledge of such matters may be surprised by my recommendation to absorb large quantities of microbes, as the general belief is that microbes are all harmful. This belief, however, is erroneous. There are many useful microbes, amongst which the lactic bacilli have an honourable place. Moreover, the attempt has already been made to cure certain diseases by the administration of cultures of bacteria. M. Brudzinsky[148] has used cultures of lactic microbes in certain intestinal diseases of infants, whilst Dr. Tissier[149] has used them in similar affections of infants and adults.

From the general point of view of this book, the course recommended consists of the absorption either of soured milk prepared by a group of lactic bacteria, or of pure cultures of the Bulgarian bacillus, but in each case taking at the same time a certain quantity of milk sugar or saccharose.

For more than eight years I took, as a regular part of my diet, soured milk at first prepared from boiled milk, inoculated with a lactic leaven. Since then, I have changed the method of preparation and have adopted finally the pure cultures which I have been describing. I am very well pleased with the result, and I think that my experiment has gone on long enough to justify my view. Several of my friends, some of whom suffered from maladies of the intestine or kidneys, have followed my example, and have been well satisfied. I think, therefore, that lactic bacteria can render a great service in the fight against intestinal putrefaction.

If it be true that our precocious and unhappy old age is due to poisoning of the tissues (the greater part of the poison coming from the large intestine inhabited by numberless microbes), it is clear that agents which arrest intestinal putrefaction must at the same time postpone and ameliorate old age. This theoretical view is confirmed by the collection of facts regarding races which live chiefly on soured milk, and amongst which great ages are common. However, in a question so important, the theory must be tested by direct observations. For this purpose the numerous infirmaries for old people should be taken advantage of, and systematic investigations should be made on the relation of intestinal microbes to precocious old age, and on the influence of diets which prevent intestinal putrefaction in prolonging life and maintaining the forces of the body. It can only be in the future, near or remote, that we shall obtain exact information upon what is one of the chief problems of humanity.

In the meantime, those who wish to preserve their intelligence as long as possible and to make their cycle of life as complete and as normal as is possible under present conditions, must depend on general sobriety and on habits conforming to the rules of rational hygiene.