PART IV

SHOULD WE TRY TO PROLONG HUMAN LIFE?

I

THE BENEFIT TO HUMANITY

Complaints of the shortness of our life—Theory of “medical selection” as a cause of degeneration of the race—Utility of prolonging human life

Although the duration of the life of man is one of the longest amongst mammals, men find it too short. From the remotest times the shortness of life has been complained of, and there have been many attempts to prolong it. Man has not been satisfied with a duration of life notably greater than that of his nearest relatives, and has wished to live at least as long as reptiles.

In antiquity, Hippocrates and Aristotle thought that human life was too short, and Theophrastus, although he died at an advanced age (he lived probably seventy-five years) lamented when he was dying “that nature had given to deer and to crows a life so long and so useless, and to man only one that was often very short.”[105]

Seneca (_De brevitate vitæ_) and later, in the 18th century, Haller, strove in vain against such complaints, which have lasted until our own days. Whilst animals have no more than an instinctive fear of danger, and cling to life without knowing what death is, men have acquired an exact idea of death, and their knowledge increases their desire to live.

Ought we to listen to the cry of humanity that life is too short and that it would be well to prolong it? Would it really be for the good of the human race to extend the duration of the life of man beyond its present limits? Already it is complained that the burden of supporting old people is too heavy, and statesmen are perturbed by the enormous expense which will be entailed by State support of the aged. In France, in a population of about 38 millions, there are two millions (1,912,153) who have reached the age of 70, that is to say, about five per cent. of the total. The support of these old people absorbs a sum of nearly £6,000,000 per annum.[106] However generous may be the views of the members of the French Parliament, many of them hesitate at the idea of so great a burden. Without doubt, men say, the cost of maintaining the aged will become still heavier if the duration of life is to be prolonged. If old people are to live longer, the resources of the young will be reduced.

If the question were merely one of prolonging the life of old people without modifying old age itself, such considerations would be justified. It must be understood, however, that the prolongation of life would be associated with the preservation of intelligence and of the power to work. In the earlier parts of this book I have given many examples which show the possibility of useful work being done by persons of advanced years. When we have reduced or abolished such causes of precocious senility as intemperance and disease, it will no longer be necessary to give pensions at the age of sixty or seventy years. The cost of supporting the old, instead of increasing, will diminish progressively.

If attainment of the normal duration of life, which is much greater than the average life to-day, were to overpopulate the earth, a very remote possibility, this could be remedied by lowering the birth-rate. Even at the present time, while the earth is far from being too quickly peopled, artificial limitation of the birth-rate takes place perhaps to an unnecessary extent.

It has long been a charge against medicine and hygiene that they tend to weaken the human race. By scientific means unhealthy people, or those with inherited blemishes, have been preserved so that they can give birth to weak offspring. If natural selection were allowed free play, such individuals would perish and make room for others, stronger and better able to live. Haeckel has given the name “medical selection” to this process under which humanity degenerates because of the influence of medical science.

It is clear that a valuable existence of great service to humanity is compatible with a feeble constitution and precarious health. Amongst tuberculous people, those with inherited or acquired syphilis, and those with a constitution unbalanced in other ways, that is to say, amongst so-called degenerates, there have been individuals who have had a large share in the advance of the human race. I need only instance the names of Fresnel, Leopardi, Weber, Schumann and Chopin. It does not follow that we ought to cherish diseases and leave to natural selection the duty of preserving the individuals which can resist them. On the other hand, it is indispensable to try to blot out the diseases themselves, and, in particular, the evils of old age, by the methods of hygiene and therapeutics. The theory of medical selection must be given up as contrary to the good of the human race. We must use all our endeavours to allow men to complete their normal course of life, and to make it possible for old men to play their parts as advisers and judges, endowed with their long experience of life.

To the question propounded at the beginning of this section of my book, I can make only one answer: Yes, it is useful to prolong human life.

II

SUGGESTIONS FOR THE PROLONGATION OF LIFE

Ancient methods of prolonging human life—Gerokomy—The “immortality draught” of the Taoists—Brown-Séquard’s method—The spermine of Poehl—Dr. Weber’s precepts—Increased duration of life in historical times—Hygienic maxims—Decrease in cutaneous cancer

Men of all times have attempted all manner of devices to bring about an increase of years, although they have not considered the problem in its general bearing.

In Biblical times it was believed that contact with young girls would rejuvenate and prolong the life of feeble old men. In the first Book of Kings it is related as follows:—

“Now King David was old and stricken in years; and they covered him with clothes, but he gat no heat.

“Wherefore his servants said unto him, Let there be sought for my Lord the king a young virgin; let her stand before the king and let her cherish him, and let her lie in thy bosom, that my lord the king may get heat” (Kings I., chap. i.).

This device, afterwards called _gerokomy_, was employed by the Greeks and Romans, and has had followers in modern times. Boerhave, the famous Dutch physician (1668-1738), “recommended an old burgomaster of Amsterdam to lie between two young girls, assuring him that he would thus recover strength and spirits.” After quoting this, Hufeland, the well-known author of “Macrobiotique” in the eighteenth century, made the following reflection:—“If it be remembered how the exhalations from newly opened animals stimulate paralysed limbs, and how the application of living animals soothes a violent pain, we cannot refuse our approval to the method.”[107]

Cohausen, a doctor of the eighteenth century, published a treatise on a Roman, Hermippus, who had died aged a hundred and fifteen years. He had been a master in a school for young girls, and his life, passed in their midst, was greatly prolonged. “Accordingly,” commented Hufeland (p. 6), “he gives the excellent advice to breathe the air of young girls night and morning, and gives his assurance that by so doing the vital forces will be strengthened and preserved, as adepts know well that the breath of young girls contains the vital principle in all its purity.”

In the Eastern half of the world equal ingenuity was exercised in the attempt to rejuvenate the body and renew the forces of man. The successors of Lao-Tsé searched for a beverage that would confer immortality and have recounted extraordinary matters concerning it.

The Emperor of China, Chi-Hoang-Ti (221-209 B.C.), displayed extreme friendliness to the Taoists, believing that these had the secret of long life and immortality. In his reign, Su-Chi, a Taoist magician, persuaded him that eastwards of China there lay fortunate islands inhabited by genii whose pleasure it was to give their guests to drink of a beverage conferring immortality. Chi-Hoang-Ti was so delighted with the news that he equipped an expedition to discover the islands.[108]

Later on, in the dynasty of the Tchengs (618-907), when Taoism had again become a religion in favour at court, efforts were made to obtain imperial patronage for the draught of immortality, and magicians were in high favour. The Taoist writers called this drink _Tan_ or _Kin-Tan_, the “golden elixir.” According to Mayers, the chief ingredients of this marvellous compound were “cinnabar, the red sulphate of mercury, and a red salt of arsenic, potassium and mother-of-pearl. The preparation of it required nine months, and it passed through nine changes. One who had drunk of it was changed to a crane, and in this form could ascend to the dwellings of the genii, there to abide with them.”[109]

The Taoists represent their saints, in the shade of willows, seeking the elixir of life, and in Chinese Buddhist temples there are placed votive cakes shaped like the tortoise, a sacred animal and the symbol of long life. Worshippers let stones of divination fall on these cakes and so ascertained if their lives were to be prolonged, promising for each subsequent year as many cakes as the divinity might demand.

The mysticism of the East reached Europe in the Middle Ages, and then, and even in modern times, drugs were used to prolong life. Cagliostro, the celebrated quack of the eighteenth century, boasted that he had discovered an elixir of life by the use of which he had survived for many thousand years.

There still exists, in some modern pharmacopœias, an “elixir ad longam vitam” compounded of aloes and other purgatives. Analogous preparations are known, such as the “vital essence of Augsburg” which is a mixture of purgatives and resins.

Serious physicians have rejected such preparations of the quacks. They have abandoned the search for a specific, and, in their efforts to prolong human life, have relied on common rules of hygiene, such as cleanliness, exercise, fresh air, and general sobriety. In our own days, Brown-Séquard is an isolated instance of a seeker for a specific against senescence. This distinguished physiologist, setting out from the view that the weakness of old men is due partly to diminution of the secretions of the testes, hoped to find a remedy in the employment of subcutaneous injections of emulsions of the testes of animals (dogs and guinea-pigs). Brown-Séquard,[110] then aged 72 years, gave himself several such injections, and declared that he found himself reinforced and rejuvenated. Since then, numbers of persons have undergone the treatment which for a time was in vogue. The observations of physicians, made on old men and sick persons, have not justified the hopes which were entertained of the mode of treatment. Fürbringer,[111] in particular, working in Germany, has discredited the injections of Brown-Séquard. However, instead of following exactly the original prescription, Fürbringer employed a testicular emulsion which had been previously raised to the boiling-point. Brown-Séquard’s method has not resisted scientific investigation, and although it is still occasionally employed in France, it has been given up in many countries.

Brown-Séquard laid stress on the efficacy of emulsions of testis as opposed to chemical substances prepared from the gland. Other scientific men, on the other hand, have attached value to such substances and in particular to an organic alkali the salt of which is known as spermine. That salt, made by Poehl of St. Petersburg, has been largely used. Several observers declare that its employment, injected in solution or even absorbed directly as a powder, has been followed by a strengthening of bodily power enfeebled by age or labour.

As I have no personal experience of spermine, I shall quote from Professor Poehl[112] some indications of its efficacy. Several physicians (Drs. Maximovitch, Bukojemsky, Krieger and Postoeff) have given injections of spermine to enfeebled old men who had lost appetite and sleep, and have noted improvement lasting for months. From the instances given, I have selected that of an old lady of ninety-five years, afflicted with severe sclerosis of the arteries, with no appetite, a bad digestion and constipation. This patient had complained for several years of sacral pains, and moreover was nearly quite deaf and suffered from periodic attacks of malarial fever. The injections of spermine, given for a period of fifteen months, restored the old lady to such an extent that she recovered her power of hearing and felt the sacral pains only slightly and after a long walk. Her general condition was highly satisfactory.

Spermine, as it has been used medically, is prepared not only from the testes of animals but from the prostate gland, ovary, pancreas, thyroid gland and spleen. The substance is not specially associated with spermatozoa but has a wide distribution in the mammalian body.

In the medical treatment of the evils of old age, testicular emulsions or spermine have not been so favoured as general hygienic measures. Dr. Weber,[113] a London medical man, has recently summarised more general measures, and his evidence is the more important as he has been able to test the efficacy of his precepts in his own case. Dr. Weber is 83 years old, and in his practice has cared for many other old men.

The following are the precepts which Dr. Weber formulated: All the organs must be preserved in a condition of vigour. It is necessary to recognise and subdue any morbid tendencies whether these be hereditary or have been acquired during life. It is necessary to be moderate in food and drink, and in all other physical pleasures. The air should be pure in the dwelling and in the vicinity. It is necessary to take exercise daily, whatever be the weather. In many cases the respiratory movements must be specially exercised, and exercise on level ground and up-hill should be taken. The persons should go to bed early and rise early, and not sleep for more than six or seven hours. A bath should be taken daily and the skin should be well rubbed, the water used being hot or cold, according to taste. Sometimes it is advantageous to use hot and cold water. Regular work and mental occupation are indispensable. It is useful to stimulate the enjoyment of life so that the mind may be tranquil and full of hope. On the other hand, the passions must be controlled and the nervous sensations of grief avoided. Finally, there must be a resolute intention to preserve the health, to avoid alcohol and other stimulants as well as narcotics and soothing drugs.

By following his own precepts, Dr. Weber has enjoyed a vigorous and happy old age. A Mde. Nausenne, who died on March 12th, 1756, at the age of 125 years, in the Dinay Infirmary (Côtes-du-Nord) explained the secret of her still greater longevity as follows: “Extreme sobriety, no worry, body and mind quite calm” (Chemin, _op. cit._, p. 101).

Hygienic measures have been the most successful in prolonging life and in lessening the ills of old age.

Although until quite recently hygiene has rested upon a very small number of scientifically established facts, and although its precepts have not been followed rigidly, none the less it has already succeeded in increasing the duration of human life. This becomes evident if we compare the mortality tables of the present day with those of the past.

There is reason to state definitely that the mortality in civilised countries has decreased on the whole in the last one or two centuries. I have taken some facts regarding this from the valuable monograph of M. Westergaard.[114] That author came to the conclusion that the mortality rate in the 19th century in civilised countries was “much lower than in most earlier centuries.” This diminution has been chiefly in infantile mortality. According to Mallet, the mortality rate of infants in the first year of their life was, in Geneva, 26 per cent. in the 16th century, and fell gradually to 16-1/2 per cent. at the beginning of the 19th century. A similar change has been reported from Berlin, Holland, Denmark and other places. However, it is not only very young infants that have shown a diminution in the death-rate. The life of old people has been prolonged to an extent equally remarkable. The following are some of the facts which support this statement. Whilst the old Protestant clergymen of Denmark at ages varying from 74-1/2 to 89-1/2 years had a mortality rate of 22 per cent. in the second half of the 18th century, the rate had sunk to 16·4 per cent. by the middle of the 19th century. This is not an isolated fact. The old clergymen of England (65 to 95 years) have also come to live longer, because in the 18th century the mortality rate was 11·5 per cent. and in the 19th century (1800-1860) only 10·8 per cent. There has been a similar decrease in the mortality rate in the members of both sexes of the Royal Houses of Europe (Westergaard, p. 284).

From 1841 to 1850, in England and Wales 162·81 individuals out of every thousand of both sexes died annually, but the corresponding figure for the period 1881 to 1890 was decreased to 153·67 per thousand.

Westergaard (p. 296) has displayed in a most useful table the mortality in the chief countries of Europe and in the State of Massachusetts, in two periods of time. In the case of old persons from 70 to 75 years, there has been a constant decrease in the death-rate, without any exceptions. The exact statistics collected by Pension Bureaus and Life Assurance Companies exhibit the same general tendency.

It cannot be disputed then that there has been a general increase in the duration of life, and that old people live longer at the present time than in former ages. This fact, however, cannot be taken absolutely, and it is still possible that in particular cases there may have been more centenarians hitherto than at present.

The prolongation of life which has come to pass in recent centuries must certainly be attributed to the advance of hygiene. The general measures for the preservation of health, although they were not specially directed to old people, have had an effect of increasing their longevity. As in the 18th century and for the greater part of the 19th, the science of hygiene was in a very rudimentary condition, we may well believe that improvement in cleanliness and in the general conditions have contributed largely to the prolongation of life. It is now a long time since Liebig said that the amount of soap used could be taken as a measure of the degree of civilisation of a people. As a matter of fact, cleanliness of the body brought about in the most simple way, by washing with soap, has had a most important effect in lessening disease and mortality from disease. In this connection, the fact recently published by Prof. Czerny,[115] a well-known German surgeon, has a special interest. Although cancer, the special scourge of old age, has increased in recent times, one form of the disease, cancer of the skin, has diminished notably. “Cancers of the skin,” Prof. Czerny says, “are met with almost exclusively on uncovered regions of the body, or on parts accessible to the hands. They develop especially where the susceptibility is increased by ulcers or scars which are easily soiled. And so it happens that in the classes where care is taken as to cleanliness cancer of the skin is very rare and certainly much more rare than it used to be.”

M. Westergaard thinks that vaccination against small-pox has been of considerable importance in lowering the death-rate in the 19th century. This, however, can have had little effect on the duration of life in old people, as deaths due to small-pox in the old are excessively rare. For instance, in the second half of the 18th century, that is to say before the introduction of Jenner’s method, the mortality from small-pox at Berlin was 9·8 per cent. of all the deaths, but of these only 0·6 per cent. were cases of persons more than fifteen years old. The rest, that is to say, 99·3 per cent. fell on children under that age. It may be supposed that most of the old people at that time were already protected by previous attacks of small-pox, contracted when they were young.

If hygiene were able to prolong life when it was little developed, as was the case until recently, we may well believe that, with our greater knowledge of to-day, a much better result will be obtained.

III

DISEASES THAT SHORTEN LIFE

Measures against infectious diseases as aiding in the prolongation of life—Prevention of syphilis—Attempts to prepare serums which could strengthen the higher elements of the organism

Attacks of infectious diseases incurred during life frequently shorten its duration and it has been observed that most centenarians have enjoyed good health throughout their lives. Syphilis is the most important of these diseases. It is not really a cause of death itself, but it predisposes the organism to the attacks of other diseases, amongst the latter being some particularly fatal to old people, such as diseases of the heart and blood-vessels (angina pectoris and aneurism of the aorta) and some malignant tumours, especially cancer of the tongue and of the mouth. To lengthen human life, it is a fundamental necessity to avoid infection by syphilis. To reach this result everything must be done to spread medical knowledge about such diseases. It is absolutely necessary to overcome the deeply rooted prejudice in favour of concealing everything relating to sexual matters. Complete information should be widely spread as to the means of protecting humanity against this awful scourge. It has now been possible to apply experimental methods to the investigation of this disease, and science has obtained a series of results of the highest practical utility. Prof. Neisser of Breslau, one of the most distinguished of modern venereal physicians, has summed up the present state of knowledge of these matters in the following lines.[116] “It is our duty as medical men,” he says, “to recommend strongly as a means of disinfection in all possible cases of contagion the calomel ointment which Metchnikoff and Roux have advised.” It is to be hoped that future generations, by following this advice, will see an enormous diminution in the number of cases of syphilis.

Syphilis, however, although a very important factor, is not alone in shortening the life of man. A very large number of persons die prematurely although they have not contracted that disease. We do not know the duration of human life before the arrival of syphilis in Europe, but there is no reason to think that it was very different from what it is to-day. We must, therefore, try to prevent as many infectious diseases as possible, and recent advances in medicine have made this task much less difficult. Pneumonia, it is true, the most common infectious disease amongst the old, cannot yet be easily avoided. All the anti-pneumonic serums which have hitherto been prepared have turned out to have little efficacy; but there is no reason to give up the hope that this problem will yet be solved.

Diseases of the heart, which are common in extreme old age, are particularly difficult to avoid, because in most cases we do not know sufficiently well their primary causes. In so far as they depend upon intemperance or infectious diseases such as syphilis, they can be avoided by the employment of suitable measures.

As the higher elements of the body in old people become weaker and are devoured by the macrophags, it seems probable that the destruction or deterioration of these voracious cells would tend to the prolongation of life. However, as the macrophags are indispensable in the struggle against the microbes of infectious diseases, and particularly of chronic disease, such as tuberculosis, it is necessary to preserve them. We must turn rather to the idea of a remedy which could strengthen the higher elements and make them a less ready prey to the macrophags.

In the “Nature of Man” (Chap. III.) in discussing the simian origin of mankind, I touched on the existence of animal serums that have the power of dissolving the blood corpuscles of other species of animals. There is now, in biological science, a new chapter upon such serums, which have been called cytotoxic serums because they are able to poison the cells of organs.

The blood and blood serum of some animals act as poisons when they are introduced into an organism. Eels and snakes, even non-poisonous snakes, are cases in point. A small quantity of the blood of a snake, an adder for instance, injected into a mammal (rabbit, guinea-pig, or mouse) soon brings about death. The blood of some mammals is poisonous to other mammals, although in a lesser degree than that of snakes. The dog is specially notable from the fact that its blood is poisonous to other mammals, whilst, on the other hand, the blood and blood serum of the sheep, goat, and horse have generally little effect on other animals and on man. It is for this reason that these animals, and particularly the horse, are used in the preparation of the serums employed in medicine.

Now, these harmless serums become poisonous when they have been taken from animals which have been first treated with the blood or the organs of other species of animals. For instance, the blood serum of a sheep which has been treated with the blood of a rabbit becomes poisonous because it has acquired the power of dissolving the red blood corpuscles of the rabbit. It is a poison in the case of the rabbit, but is harmless to most other animals. The injection of the rabbit’s blood into the sheep has conferred on the sheep a new property which comes into operation only with regard to the red blood corpuscles of the rabbit. We have here to do with something analogous to what has been observed in the cases of serums used to arrest infectious disease. When the bacilli of diphtheria, or their products, have been injected into horses, there is produced an anti-diphtheric serum, capable of curing diphtheria, but powerless against tetanus or plague. After M. J. M. Bordet of the Pasteur Institute had made his discovery of serums that had acquired the power of dissolving the red blood corpuscles of other animals, the attempt was made to prepare similar serums directed against all the other elements of the body, such as white blood corpuscles, renal and nervous cells. In the course of these investigations it was proved to be necessary to employ a certain dose of the serum in order to obtain the poisonous result. If smaller quantities of the poisonous dose were used, the reverse effect was produced. Thus a serum, strong doses of which dissolved the red blood corpuscles and so made them less numerous in the blood, increased the number of these when given in very small doses.

M. Cantacuzène was the first to establish this fact in the case of the rabbit, whilst M. Besredka and I myself did it in the case of man.[117] Since then M. Bélonovsky of Cronstadt has confirmed the result on anæmic patients, treating them with small quantities of serum. He has been able to produce in them an increase in the number of the red blood corpuscles, and in the quantity of the red colouring matter (hæmoglobin) in the blood. Later on M. André[118] devoted much attention to this matter at Lyons. He prepared a serum by injecting human blood into animals and made use of it in the case of several persons who suffered from anæmia from different causes. In the case of patients, the anæmic condition of which had hitherto remained stationary, Dr. André found a sudden increase in the number of red corpuscles after injecting small doses of the serum. M. Besredka, in the case of laboratory animals, increased the number of white corpuscles by injecting them with a small quantity of a serum, strong doses of which destroyed these cells.

These facts are only a special case of the general rule that small doses of poisons increase the activity of the elements that are killed by large doses. In order to increase the activity of the heart, medical men give successfully small doses of cardiac poisons such as digitalis. As a commercial process, the activity of yeasts is increased by submitting them to weak doses of substances (fluoride of sodium) which, given in larger quantities, would kill them.

My general conclusion from these facts is that it is logical to lay down the principle that the higher elements of our body could be strengthened by subjecting them to the action of small doses of the appropriate cytotoxic serums. There is, however, much difficulty in putting this into practice. It is quite easy to obtain human blood to inject into animals with the object of preparing a serum which can increase the number of red corpuscles. On the other hand, it is extremely difficult to get human bodies sufficiently fresh to use them for a practical purpose. According to law, _post mortem_ examinations can be made only after an interval of time in course of which the tissues have changed; besides, the organs obtained in this way are frequently affected by injuries or diseases militating against their use. Even in Paris, with its three million inhabitants, it is extremely rare that there is a good opportunity for the preparation of human cytotoxic serums. In two or three years, during which Dr. Weinberg has collected the organs from human bodies fairly fresh, he has been unable to obtain sufficiently active serums.

The best results have been obtained from new-born infants which have been killed by some accident in the process of child-birth, as in them the organs are in a normal state. However, owing to the advance in the practice of obstetrics, such accidents, already infrequent, are becoming extremely rare. In such conditions we may have to wait long before getting a positive result, unless the future will find some method of obtaining the necessary materials for this difficult and interesting purpose.

As it is so difficult to prepare a remedy which can strengthen the weakened higher elements of the body, it may be easier to find a means of preventing the weakening which interferes so much with our desire to live long. As the products of microbes are the most active agents in deteriorating our tissues, we must look towards them for the solution of the problem.

IV

INTESTINAL PUTREFACTION SHORTENS LIFE

Uselessness of the large intestine in man—Case of a woman whose large intestine was inactive for six months—Another case where the greater part of the large intestine was completely shut off—Attempts to disinfect the contents of the large intestine—Prolonged mastication as a means of preventing intestinal putrefaction

The general measures of hygiene directed against infectious diseases play a part in prolonging the lives of old people, but, in addition to the microbes which invade the body from outside, there is a rich source of harm in the microbes which inhabit the body. The most important of these belong to the intestinal flora, which is abundant and varied.

The intestinal microbes are most numerous in the large intestine. This organ, which is useful to mammals the food of which consists of rough bulky vegetable matter, and which require a large reservoir for the waste of the process of digestion, is certainly useless in the case of man.[119] In the “Nature of Man” I have dealt with this question at length, as it was an important example of what I regard as the disharmonies of the human constitution. A case upon which I have always laid great stress is that of a woman who lived for thirty-seven years, although her large intestine was atrophied and inactive, as this seems to be a remarkable proof of the uselessness of the organ in the human body. The small size or complete absence of the large intestine in many vertebrates confirms my conclusion. None the less, some of my critics think that my argument is incomplete. To strengthen it, I may call their attention to a medical observation which is as valuable as if it had been an experiment. It relates to a woman, sixty-two years old, a patient of Prof. Kocher at Berne. She had been suffering from a strangulated hernia associated with gangrene of part of the intestine, and had to be operated upon suddenly.

The gangrenous portion of the ileum having been removed, the healthy part was implanted in the skin so as to form an artificial aperture through which waste matter from the food passed to the exterior without traversing the large intestine. Although the patient was old and seriously ill, the operation, performed by M. Tavel, was quite successful. Six months later, in a new operation, the small intestine was rejoined to the large intestine so that the fæces were again able to pass to the exterior by the natural channel. In this case, then, the large intestine was thrown out of use for half a year, not only without injury to the general health, but with the result that the patient was completely cured and gained in weight. MM. Macfadyen, Nencki, and Mde. Sieber[120] studied the digestive processes in the small intestine and the nutritive metabolism, and determined that these were active and healthy, the absence of intestinal putrefaction, that evil of the constitution, being specially favourable.

In six months of non-action, the part played by an organ can be satisfactorily estimated. M. Mauclaire,[121] however, has put on record a case the history of which was longer. In 1902 he operated on a young woman and produced an artificial anus, there being no escape of fæcal matter by the ordinary channel. Ten months later M. Mauclaire operated a second time and shut off a portion of the intestine. He left the artificial anus, but cut across the lower end of the small intestine and inserted it near the iliac end of the descending colon (Fig. 19). For several days after the operation the fæces were passed by the normal aperture, as the small intestine now communicated directly with the large intestine, near the rectum. This condition, however, did not persist, for the fæcal matter began to flow back through the excluded portion of the large intestine, so reaching the artificial anus, and causing inconvenience. Giving up the hope that this would cease, M. Mauclaire performed a third operation twenty months later. He cut across the large intestine near the point where the small intestine had been artificially led into it (Fig. 20), so dividing the digestive tube into two parts, one of which remained in communication with the natural anus, whilst the other, consisting of nearly the whole of the large intestine, communicated with the exterior by the artificial anus. In the new state of affairs, the food refuse passed directly into the terminal portion of the large intestine, and thence, by way of the rectum, to the exterior through the normal anus without being able to pass up the large intestine towards the artificial anus. In this last operation about a yard of the small intestine and the greater part of the large intestine, the cæcum, and ascending, transverse and descending colons were removed from activity.

By the kindness of M. Mauclaire, I have been able to watch his patient during the last four years. I satisfied myself that after the supposed exclusion of the large intestine, food dejecta ascended the colon and emerged by the artificial anus. There was such an accumulation of waste in the large intestine that fragments did not emerge until three weeks after the meal of which they had formed part. It was only after the final operation, that in which the large intestine was separated, that the dejecta escaped only by the natural anus, whilst a little mucus containing microbes was passed through the artificial aperture. Even three years after the operation, mucus continued to escape by the latter aperture, it being shown thus that after the large intestine had ceased to be a channel for the fæces, its walls continued to secrete although otherwise it had lost its function completely. Nevertheless the condition of this patient improved and she lived perfectly well without a functional large intestine. She takes food well but has to go to stool three or four times a day and has a tendency to diarrhœa. The excreta are smooth and often nearly liquid, especially after fruit has been eaten.

The case I have been describing, and which I am still keeping under observation, demonstrates once more the uselessness of the human large intestine; it should convert the most sceptical critic. But it also shows that the suppression of nearly the entire large intestine for several years does not completely get rid of the intestinal flora. Even without this evidence, however, I do not suggest that removal of the large intestine can be thought of as a means to prevent the pernicious effect of the intestinal flora.

Is it possible, without operative interference, to take direct action against the intestinal flora by the use of antiseptics? Consideration of this is already ancient history. When the theory that the intestine was a source of auto-intoxication was propounded, M. Bouchard[122] made the attempt to cure such cases by disinfecting the digestive tube with [Greek: b]-naphthol. He found, however, that that antiseptic, like many others, not only did not completely disinfect the intestine but sometimes had a harmful effect on the body.

M. Stern[123] has shown, in an elaborate memoir, that such antiseptics as calomel, salol, [Greek: b]-naphthol, naphthaline, and camphor, when administered in quantities compatible with health, do not disinfect the digestive tube at all. More recently M. Strasburger[124] has shown that when naphthaline has been given in quantities sufficient to impart its odour to the fæces, the intestinal microbes, so far from being diminished, are even increased in numbers. On the other hand, after meals consisting of milk to which there has been added an antiseptic in the proportion of a quarter of a gram to the litre, the intestinal microbes are really reduced in number. Strasburger obtained his best results with tanocol. Two persons who used, according to this method, three to six grams of tanacol per day, displayed a notable reduction in quantity of the intestinal flora.

Strasburger’s conclusion was that “the attempt to destroy the intestinal microbes by the use of chemical agents has little chance of success.” It cannot be denied that under special circumstances it is possible to decrease the number of microbes, especially in the small intestine. But this result is small and may be followed by the contrary effect, for the natural means of defence of the intestine against microbes are weakened, and the intestine itself may be harmed more than the microbes.

Strasburger, moreover, is no convinced advocate of the use of purgatives. The diminution of the sulpho-conjugate ethers in the urine, which certainly may follow the use of purgatives, does not necessarily indicate reduced putrefaction in the intestine, but may point only to a lessened absorption of the bacterial products. Such an interpretation is supported by an observed fact; in the case of a dog belonging to Strasburger, which had a fistula of the small intestine, the diarrhœa induced by calomel was accompanied by an indubitable increase in the total quantity of intestinal microbes.

Strasburger thinks that the most favourable results can be obtained by aiding the intestine in the discharge of its normal function. If it can be brought to digest the food more completely, there is the less pabulum left for the microbes. A similar result can be reached by lowering the amount of food taken, and to this course the beneficial effects of starvation in acute diseases of the intestine may be attributed.

The general conclusion, reached after many experiments on the disinfection of the intestine, is unfavourable. Very little is to be expected from the method. None the less I cannot regard the matter as definitely settled. Cohendy has investigated the effect on the intestinal flora of thymol which was administered in several cases with the object of destroying parasites. From nine to twelve grammes of thymol were administered to each patient in the space of three days, and there was a notable antiseptic effect, Cohendy believing that the quantity of microbes had been reduced to a thirteenth.

Such facts prove only that the antiseptic treatment is available up to a certain point. To attain the results, however, such large quantities must be used that the treatment can be applied only in special cases and at long intervals. More use can be made of simple purgatives which do not kill the microbes but eliminate them by the normal channel. It has been urged repeatedly that calomel, which is often used as a purgative, acts also as an intestinal antiseptic; but it is probable that its influence in reducing the intestinal flora is merely mechanical. It has been shown that calomel, like some other purgatives, lessens intestinal putrefaction, the evidence being the decrease in the sulpho-conjugate ethers in the urine. But although the diarrhœa induced by purgatives generally has such a result, spontaneous diarrhœas such as those of typhoid fever and of intestinal tuberculosis are associated with increased putrefaction.[125]

It is clear, however these matters may be settled, that regular activity of the bowels, increased by the occasional use of purgatives, must diminish the formation of intestinal poisons, and therefore also the damage done by these to the higher elements of the body.

When I asked the relatives of Mde. Robineau if they could tell me of any special circumstance which in their opinion had contributed to the extreme duration of the life of this old lady, they replied as follows:—“We are convinced that a slight bodily derangement, present for the last fifty years, has tended to prolong the life of the old lady. It cannot be said that she has suffered from diarrhœa, but she has been often subject to frequent calls of nature.” It was most remarkable that the old lady showed no traces of sclerosis of the arteries. I may mention the strongly contrasting case of one of my old colleagues to whom a natural desire to empty the bowels came only once a week. A more frequent call was a sign of illness in his case. Now sclerosis of the arteries appeared in so marked a form that he died from it before he had reached the age of fifty years. This may be added to the list of facts which point to a close association between sclerosis of the arteries and the functions of the digestive tube.

Recently, at the suggestion of Mr. Fletcher,[126] the advantage of eating extremely slowly has been recognised, the object being to prepare for the utilisation of the food materials, and to prevent intestinal putrefaction. Certainly the habit of eating quickly favours the multiplication of microbes round about the lumps of food which have been swallowed without sufficient mastication. It is quite harmful, however, to chew the food too long, and to swallow it only after it has been kept in the mouth for a considerable time. Too complete a use of the food material causes want of tone in the intestinal wall, from which as much harm may come as from imperfect mastication. In America, where Fletcher’s theory took its origin, there has already been described under the name of “Bradyfagy” a disease arising from the habit of eating too slowly. Dr. Einhorn,[127] a well-known specialist in the diseases of the digestive system, has found that several cases of this disease were rapidly cured when the patients made up their minds to eat more quickly again. Comparative physiology supplies us with arguments against too prolonged mastication. Ruminants, which carry out to the fullest extent Mr. Fletcher’s plan, are notable for extreme intestinal putrefaction and for the short duration of their lives. On the other hand, birds and reptiles, which have a very poor mechanism for breaking up food, enjoy much longer lives.

Prolonged mastication, then, cannot be recommended as a preventative of intestinal putrefaction any more than the surgical removal of the large intestine or the disinfection of the digestive tube. The field lies open for other means which may probably solve the problem more completely and more practically.

V

LACTIC ACID AS INHIBITING INTESTINAL PUTREFACTION

The development of the intestinal flora in man—Harmlessness of sterilised food—Means of preventing the putrefaction of food—Lactic fermentation and its anti-putrescent action—Experiments on man and mice—Longevity in races which use soured milk—Comparative study of different soured milks—Properties of the Bulgarian _Bacillus_—Means of preventing intestinal putrefaction with the help of microbes

At birth the human intestine is full, but contains no microbes. Microbes very soon appear in it, because the meconium, the contents of the intestines of new-born children, composed of bile and cast-off intestinal mucus cells, is an excellent culture medium for them. In the first hours after birth, microbes begin to reach the intestine. In the first day, before the child has taken any food whatever, there is to be found in the meconium a varied flora, composed of several species of microbes. Under the influence of the mother’s milk this flora is reduced and comes to be composed almost entirely of a special microbe described by M. Tissier and called by him _Bacillus bifidus_.

The food, therefore, has an influence on the microbes of the intestine. If the child be fed with cow’s milk, the flora is richer in species than in the case of a child suckled by its mother. Later on, also, the flora varies with the food, as has been proved by MM. Macfadyen, Nencki, and Mde. Sieber in the case of a woman with an intestinal fistula. The dependence of the intestinal microbes on the food makes it possible to adopt measures to modify the flora in our bodies and to replace the harmful microbes by useful microbes. Unfortunately, our actual knowledge of the intestinal flora is still very imperfect because of the impossibility of finding artificial media in which it could be grown. Notwithstanding this difficulty, however, a rational solution of the problem must be sought.

Man, even in the savage condition, prepares his food before eating it. He submits much of it to the action of fire, thus notably lessening the number of microbes. Microbes enter the digestive tube in vast numbers with raw food, and in order to lessen the number of species in the intestines, it is important to eat only cooked food and to drink only liquids that have been previously boiled. In that way, although we cannot destroy all the microbes in the food, because some of them can withstand the temperature of the boiling point of water, we can kill the great majority of them.

It has sometimes been supposed that cooked or completely sterilised food (that is to say food that has been subjected to a temperature of from 248°-284° Fahr.) is harmful to the organism and that much of it is not well digested. From this point of view protests have been made against the feeding of infants with sterilised milk or even with boiled milk. Although in certain cases sterilised milk is not well supported by infants, it cannot be doubted but that boiled milk and cooked food are generally successful. The large number of children brought up successfully on boiled cow’s milk and the health of travellers in arctic regions are ample proof of this. I have been told by M. Charcot that in his voyage to the antarctic regions, he and his companions lived entirely on sterilised food, or on cooked food such as the flesh of seals and penguins. As they had no green food nor fresh fruit, the only raw food that they ate was a little cheese. Living under these conditions, all the members of the expedition enjoyed good health, and there was no case of digestive disturbance in the whole period of sixteen months.

It is obvious that abstaining from raw food, and so reducing largely the entrance of new microbes, by no means causes the disappearance of the intestinal flora already existing. We must reckon with that and with the evil that it does by weakening the higher cells of the tissues. As the part of the flora that does most damage consists of microbes which cause putrefaction of the contents of the intestine and harmful fermentations, particularly butyric fermentation, it is against these that our efforts must be directed.

Long before the science of bacteriology was in existence, men had turned their attention to methods of preventing putrefaction. Food, especially if it be kept in a warm place or in a moist atmosphere, soon begins to putrefy and to become unpleasant to the taste and dangerous to the health. Everyone has known cases of poisoning from putrid flesh or other food material. Foà,[128] the explorer of Central Africa, has related that once, when they were starving, he and his men came on the putrefying body of an elephant. The negroes rushed to lay hold of the carrion, but Foà tried to dissuade them, explaining that to eat flesh in such a state was as bad as taking poison. All did not listen to him, and three negroes, who had taken pieces of the body, swallowed them before they had been properly cooked. All three died in a few days, with the neck and throat swollen, the tongue almost paralysed, and the abdomen inflated.

In another case, sausages made of putrid horse flesh caused an epidemic at Rohrsdorf, in Prussia, in 1885.[129] About forty people fell ill after having eaten the sausages, which, according to witnesses, were green in colour, smelt badly, and had a revolting appearance. One person died, whilst the others recovered after cholera-like symptoms. It is true that all putrefying food does not produce the same effect. MM. Tissier and Martelly[130] found no digestive trouble after having eaten food that was quite putrid. Everyone knows that the Chinese prepare a dish particularly pleasant to gourmets by allowing eggs to putrefy. Some decaying cheeses are harmful to the health, but others can be eaten with impunity. The reason of this is that whilst putrefying food may contain microbes and dangerous toxins, it does not contain them in all cases. On the other hand, we must take into account the different susceptibilities of people to the harmful action of microbes and their products. Some can swallow without any evil result a quantity of microbes which in the case of other individuals would produce a fatal attack of cholera. Everything depends upon the resistance offered to the microbes by the invaded organism.

Experiments on animals fed on putrefying food have also given varied results. Some animals eat it without any harm resulting, others have attacks of vomiting and show such a repugnance that it is impossible to continue the experiment.

Not only flesh and other animal substances, but vegetables can undergo putrefaction and fermentation (butyric) which make it dangerous to eat them. Many accidents have occurred in man as the result of deteriorated preserved fruit. Vegetables, preserved in silos to feed cattle, sometimes go wrong. “If, for instance, rainy days come after sunny days, so that the uncovered fodder is wetted again, the resulting ensilage is poor and has an extremely unpleasant butyric odour, so that the animals turn from it.” Sometimes the fodder grows black in the silo, and acquires a special smell. “The animals will take it only in the absence of other food; their excreta become black, and if they are kept on such a diet for a time they waste in a marked manner.”[131]

In popular practice, the value of acids for preserving animal and vegetable food and for preventing putrefaction has long been recognised. Meats of all kinds, fish and vegetables have been “marinated” with vinegar, as the acetic acid in that substance, the product of bacteria, wards off putrefaction. If the materials which it is desired to preserve give off acids themselves, the addition of vinegar may be unnecessary. For this reason some animal products such as milk, or vegetables rich in sugar become acid spontaneously and so can be preserved. Soured milk can be made into many kinds of cheese, and these last for longer or shorter times. Many vegetables can undergo a natural process of souring, when they “keep” without difficulty. Thus cabbage becomes “sauerkraut” and beetroot and cucumbers pass into an acid state. In many countries, as for instance in Russia, the use of acidified vegetables is of great importance in the food-supply of the populace. Fresh fruit and vegetables cannot be obtained in the long winters, during which the people consume large quantities of cucumbers, melons, apples, and other fruits which have undergone an acid fermentation in which lactic acid is the chief product. During summer, milk, which acidifies readily, is the chief source of acid materials for consumption. The chief beverage is “kwass,” of which black bread is the main ingredient, and this passes through not only an alcoholic fermentation, but an acidifying change in which lactic acid is the most important product.

Rye bread, the chief food of the populace, is also a product of fermentations amongst which the lactic acid fermentation is most important, but in other kinds of bread also there is a fermentation in which some of the sugar is transformed to lactic acid.

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.