Chapter X: Part II: Longevity in the Animal Kingdom (2)

The ill-health which follows retention of fæcal matter is certainly due to the action of some of the microbes of the gut. There are difficulties, however, in determining the precise mode of action of these microbes. It is generally believed that they form poisonous substances which are absorbed by the walls of the intestine and so pass into the system. The phrase auto-intoxication as applied to infants, women in labour, and patients affected with diseases of the heart, liver, or kidneys, is based on this interpretation of the morbid processes involved. Attempts have been made to isolate and study the poisons in question, but there are many difficulties in the way. To distinguish between the actions of the poisons and of the microbes themselves, the latter have been destroyed by heat or by antiseptics, or been removed by filtration. Such methods, however, may alter the poisons and so are inconclusive. MM. Charron and Le Play[53] have tried to obtain exact results by heating the intestinal microbes to a temperature of about 136° Fahr., a process which probably does not seriously deteriorate the microbial poisons. Such material, injected into the veins of rabbits in large quantities, rapidly produced death, or in smaller quantities, proportionate ill-health.

Kukula[54] has tried to produce this toxic action in animals, employing microbial secretions obtained from cases of intestinal obstruction. He succeeded in producing serious symptoms, such as vomiting and curvature of the neck and back, in fact, precisely the sequence of events familiar in cases of obstruction of the bowels or other retentions of fæcal matter.

Some of the products of the intestinal flora are undoubtedly toxic, such as the benzol derivatives (phenol, etc.) ammonium and other salts. Many of these toxins have been insufficiently studied, but it is well known that certain of them can be absorbed by the wall of the gut and act as poisons. A well known case is the toxin of botulism which was isolated and studied by M. van Ermenghem.[55] The poison, the product of a microbe which causes serious intestinal disturbance, is so fatal that a single drop given to a rabbit produces death after symptoms similar to those observed in cases of human beings poisoned by stale food. Butyric acid and the products of albuminous putrefaction are amongst the most pernicious of the microbial poisons produced in the large intestine. It is familiar that digestive disturbance is frequently associated with discharges of sulphuretted hydrogen and putrid excreta, and there is no doubt but that the microbes of putrefaction are the cause of these symptoms.

It has been assumed for long that the retention of fæcal matter tends to putrefactive changes in the intestines, and that the evil consequences of constipation are due to this. Recently, however, bacteriologists have criticised this accepted view, on account of the small number of microbes found in the excreta of constipated persons. Strasburger was the first to establish the fact, and his associate, Schmidt, showed that putrefaction did not follow when readily putrescible substances were infected with material taken from cases of constipation. However, notwithstanding the exactness of these facts, I cannot accept the inference which has been drawn from them. The excreta discharged naturally in cases of constipation do not give a correct indication of the conditions inside the gut; whilst such matter contains few microbes, the substance removed after injection by an enema is extremely rich in bacteria. Moreover, analysis of the urine, in cases of constipation, shows an excess of the sulpho-conjugate ethers which are known to be products of intestinal putrefaction.

Not only is there auto-intoxication from the microbial poisons absorbed in cases of constipation, but microbes themselves may pass through the walls of the intestine and enter the blood. In the maladies that are the result of constipation some of the symptoms recall those of direct infection, and it is highly probable that, if special investigations were made, microbes of intestinal origin would be found in the blood of the sick children and the pregnant or parturient women whose symptoms I have described above.

The question as to the passage of microbes through the intestinal walls is one of the most controversial of bacteriological problems, and there is little agreement in the numerous publications regarding it. None the less, it is far from impossible to get a general idea of what goes on in an intestinal tract richly charged with microbes.

Although the intestinal wall in an intact state offers a substantial obstacle to the passage of bacteria, it is incontestable that some of these pass through it into the organs and the blood. Numerous experiments performed on different kinds of animals (horses, dogs, rabbits, etc.) show that some of the microbes taken with food traverse the wall of the alimentary canal and come to occupy the adjacent lymphatic glands, the lungs, the spleen and the liver, whilst they are occasionally found in the blood and lymph. Discussion has taken place as to whether the passage takes place when the wall of the gut is absolutely intact or only when it is injured to however small an extent. It would be extremely difficult to settle the question definitely, but it is easy to see that it has little practical bearing. It is known that the wall of the gut is damaged extremely easily, so that the bluntest sound can hardly be passed into the stomach without making a wound through which microbes can pass into the tissues and blood. In the ordinary course of life, the delicate wall of the gut must often undergo slight wounding, and the frequent presence of microbes in the mesenteric ganglia of healthy animals shows clearly what takes place.[56]

It is indubitable, therefore, that the intestinal microbes or their poisons may reach the system generally and bring harm to it. I infer from the facts that the more a digestive tract is charged with microbes, the more it is a source of harm capable of shortening life.

As the large intestine not only is the part of the digestive tube most richly charged with microbes, but is relatively more capacious in mammals than in any other vertebrates, it is a just inference that the duration of life of mammals has been notably shortened as the result of chronic poisoning from an abundant intestinal flora.

IV

MICROBES AS THE CAUSE OF SENILITY

Relations between longevity and the intestinal
flora—Ruminants—The Horse—Intestinal flora of
birds—Intestinal flora of cursorial birds—Duration
of life in cursorial birds—Flying mammals—Intestinal
flora and longevity of bats—Some exceptions to the
rule—Resistance of the lower vertebrates to certain
intestinal microbes

In the actual state of our knowledge it is impossible to make a final examination of my hypothesis, as there are many factors about which we are incompletely informed. Nevertheless, it is possible to confront the hypothesis with a large number of accurately established facts.

Although the life of most mammals is relatively short, there are to be found in the group some which live relatively long, as well as others whose life is short. The elephant is an example of the long-lived mammals, whilst ruminants are short-lived forms. In the last chapter, I stated that sheep and cattle became senile at an early age, and did not live long. They are striking exceptions to the rule according to which the duration of life is in direct relation with the size and length of the period of growth. The cow, which is much larger than a woman, and the time of gestation of which is about the same, or a little longer, acquires its teeth at four years old, and becomes senile at an early age; it is quite old at between sixteen and seventeen, an age when a woman is hardly adult; at the age of thirty, practically the extreme limit for bovine animals, a woman is in full vigour.

The precocious old age of ruminants, the constitution of which is well understood, and which are carefully tended, coincides with an extraordinary richness of the intestinal flora. Food remains for a long time in the complicated stomach of these animals, and afterwards the digested masses remain still longer in the large intestine. According to Stohmann and Weiske,[57] in the case of sheep it is a week until the remains of a particular meal have finally left the body of the animal. The excreta of sheep, normally solid, do not betray any special putrefaction in the intestine, but if the body is opened there is abundant evidence of the process. The intestinal contents are richly charged with microbes and give off a strong odour of putrefaction. It is not surprising that under these conditions, the life of sheep should be short.

Another large herbivorous animal, the horse, also dies young, after a premature old age. Although it does not ruminate and possesses a simple stomach, the process of digestion is slow, and enormous masses of nutritive material accumulate in the huge large intestine. Ellenberger and Hofmeister[58] have shown that food remains in the alimentary canal for nearly four days. It remains in the stomach and the small intestine only 24 hours, but about three times as long in the large intestine. This is remarkably different from what happens in the case of birds, in which there is no stagnation during the passage of food through the digestive canal.

The structure of birds is adapted for flight, the body being as light as possible, many of the bones and the cavities of the body containing air-sacs. The absence of a bladder and of a true large intestine prevents the accumulation of excreta, these being ejected almost as rapidly as they are formed. The process of ejection, which takes place often in birds, is not so inconvenient as in mammals. The hind limbs are not used in flight, so that they offer no obstacle to evacuation. Thus birds may discharge their droppings while flying.

Such structure and habits make it not surprising that the alimentary canal of many birds contains only a scanty intestinal flora. Parrots, for instance, which are remarkably long-lived birds, harbour very few microbes in the intestine. The small intestine contains almost none, the rectum so few that the fæcal matter appears to be formed of mucus, the waste of the food, and only a very few microbes. M. Michel Cohendy, who has examined the intestinal flora at the Pasteur Institute, was unable to isolate more than five different species of microbes living in the alimentary canal of parrots.

Even in birds of prey which feed upon putrid flesh, the number of microbes in the intestine is remarkably limited. I have investigated the case of ravens which I fed on flesh which was putrid and swarming with microbes. The droppings contained very few bacteria, and it was specially remarkable that the intestines had not the slightest smell of putrefaction. Although the opened body of a herbivorous mammal, such as a rabbit, gives off a strong smell of putrefaction, the body of a raven with the digestive tube exposed has no unpleasant smell. This absence of putrefaction in the intestine is probably the reason of the great longevity of such birds as parrots, ravens, and their allies.

It might be said, however, that the long duration of life in birds is due to the organisation of these animals, rather than to the scantiness of their intestinal flora. To meet this objection, it is necessary to turn to the case of cursorial birds.

There are some birds incapable of flight, the wings of which are badly developed, but which have strong limbs, and can run with great rapidity. Ostriches, cassowaries, rheas, and tinamous, are well known examples of cursorial birds. They live on the surface of the ground, and their habits resemble those of mammals. When they are attacked by enemies, they escape by running so quickly that some of them (ostriches and rheas) outstrip even a horse. However, like mammals, they cannot discharge their secretions when they are running quickly. Tinamous (_Rhynchotus rufescens_), which I have observed in captivity, however quickly they may be running, stop abruptly to discharge their excretions. M. Debreuil, at my request, made observations on this matter, and assured me that the tinamous and rheas (_Rhea americana_) in his park always stood still for this purpose. He has noticed that the droppings, however abundant, were always deposited in heaps. With regard to ostriches, M. Rivière, director of the experimental Gardens at Hamma, Algeria, has been kind enough to give me the following information. “The discharge of excreta,” he said in a letter in January, 1901, “is less frequent than in other birds, but the comparatively small size of the enclosures here makes it impossible for me to assert that the animal could discharge its droppings if it were running for a length of time; _a priori_ I should think that this did not happen. Normally the bird stands still for defæcation, the tuft of feathers on the tail is lifted up, and there is a violent contraction of the abdominal muscles before the sphincters of the cloaca are suddenly opened to discharge the excrement with violence.”

I believe that the remarkable development of the large intestine in these running birds has been acquired to obviate the danger which is caused by the animal having to stop for defæcation. Although the huge cæca of these birds have a digestive function, particularly on plants rich in cellulose, I cannot think that the cæca of cursorial birds have been developed for digestion. As a matter of fact, some birds which are not cursorial live on the same kind of food (herbage, seeds, and insects) and have much smaller cæca, the cæca indeed, in some, for instance, the pigeons, being quite rudimentary.

It is not surprising that the accumulation of food material in the large intestine of running birds is associated with the presence of an extremely rich intestinal flora. Microscopic examination of the excrement of such birds shows this at once. Although the intestinal contents and excrement of many other birds show the presence of very few microbes, belonging to a small number of species, the same materials taken from running birds show enormous quantities of microbes, belonging to a large number of species. In the cæcum of the rhea (Fig. 14) there are bacterial threads, spirilla, bacilli, vibrios, and many kinds of cocci. In the tinamous, the intestinal flora is if possible even richer. According to the statistical investigations of M. Michel Cohendy, the quantity of intestinal microbes in cursorial birds is not less than that found in mammals, even in man.

If I am correct in the view that I have been explaining, cursorial birds, on account of their rich intestinal flora, ought to have a shorter duration of life than that of flying birds. I will now turn to this side of the question. Amongst cursorial forms, there are some of the largest living birds, ostriches being actually the largest living birds, whilst an extinct running bird, the _Aepyornis_ of Madagascar, was the largest known bird. According to the rule that large animals live longer than small animals, ostriches should be able to reach a great age. The facts, however, are against this. M. Rivière, who rears ostriches in Algeria, and has a great experience of them, writes to me as follows: “I have no confidence in the stories about the longevity of the ostrich which were told me in the Sahara; they rest on no facts. My personal observation is not very large, but it is quite exact. Some of the ostriches which have been hatched here have lived for 26 years. I do not estimate the duration of life of this bird at more than 35 years, and only one case of this age have I seen myself in 20 years. The bird was a female, a good layer and sitter; she died of old age, showing all the signs of decrepitude, the skin excoriated and lumpy, the feathers degenerate and dry. The bird laid eggs until nearly the end of her life, but at irregular intervals, and the shells were granular instead of being smooth and polished.”

In a farm near Nice, where ostriches are reared, there was recently an old male called “Kruger,” which was supposed to be 50 years old.[59] Countess Stackelberg has been good enough to try to get information for me about this, and informs me that although they have not exact knowledge at the farm, they believe that it must be 50 years old. M. Rivière thinks this statement very surprising, and has nothing in his own long experience to confirm it.

The facts which I have been able to get together do not attribute a long life to other running birds. Gurney mentions that a cassowary (_Casuarius westermanni_) lived 26 years in the Zoological Gardens of Rotterdam, and that three Australian emus (_Dromaeus novae-hollandiae_) had lived in the same Gardens for 28, 22, and 20 years. M. Oustalet (_Ornis_, 1899, vol. x, p. 62) mentions another emu of the same species which died in London at the age of over 23 years. The rhea (_Rhea americana_), another large running bird, does not live so long. “Boecking thinks that its duration of life should be set down at from 14 to 15 years. According to him, many of these birds die of old age.” (Brehm, _Oiseaux_, vol. ii, p. 517).

It is striking to compare the short life of cursorial birds, which nevertheless thrive and reproduce in captivity, with the remarkable longevity of so many other birds (parrots, birds of prey) which, although they are much smaller, have been kept alive for from 80 to 100 years. It would be difficult to find a more striking argument in favour of the view that richness of the intestinal flora shortens life. When birds become adapted to terrestrial life and acquire a huge large intestine in which microbes can abound, their duration of life is diminished.

Just as some birds, losing the aerial mode of life, have come to resemble mammals, so also some mammals have become flying animals, provided with wings and in some respects resembling birds. Bats are the most familiar instance. The large intestine, which is extremely useful to running animals, not only ceases to be an advantage but is harmful to flying creatures, insomuch as it increases the weight of the body uselessly. Bats, accordingly, have no cæcum whilst the large intestine is changed in structure and function. Instead of being a capacious tube, serving as a reservoir for the refuse of the food, the large intestine of bats has the same diameter as the small intestine. Its structure is nearly identical. It is provided with glands, and as I have already mentioned in the last chapter, it digests the food in the same way as the small intestine. In fact, the large intestine has become simply a part of the small intestine, the total length of the gut being reduced. Bats, therefore, can no longer retain their secretions but have to empty the intestine almost as often as most birds. I find that Indian fruit bats (_Pteropus medius_) discharge their excreta very often. Microscopic examination shows that there is an absence of microbes quite unusual in the case of a mammal. The alimentary canal of bats is nearly aseptic, containing only a few single bacteria. I have fed these fruit bats with the same food (carrots) which I have given to rabbits, guinea pigs, and mice; whilst the bats accomplished the process of digestion in 1-1/2 hours, and deposited excreta containing fragments of carrot, the rodents took very much longer for digestion and large quantities of waste matter accumulated in the cæca. The intestinal flora too, although the food in each case was the same, showed remarkable differences in these animals. It was almost absent in the bats, whilst in the rabbits, guinea-pigs and mice it consisted of a mass of microbes of different species. The excrement of the bats had no unpleasant odour, and the digestive canal of these bird-like mammals was free from putrefaction. Fruit bats fed upon fruit discharged excreta with a pleasant odour of apples and bananas. We have seen that birds which live a life similar to that of mammals acquire a rich intestinal flora and do not live so long as aerial birds. It would be extremely interesting to ascertain the duration of life of bats, mammals which live like birds and have a very scanty intestinal flora. I have been unable to get any exact information as to the duration of life of the true bats, that is to say, the insectivorous bats, as all the requests that I have addressed to specialists have proved fruitless. It appears, however, that it is a popular belief that bats live long. There is a Flemish phrase: “as long-lived as a bat,” and a similar phrase is common in Little Russia.

As for the fruit-eating bats, I have been able to ascertain that even in captivity, where the conditions are unfavourable to them, the duration of life is relatively long. I have had in my own possession a fruit bat (_Pteropus medius_) which was bought in Marseilles 14 years ago. It showed no signs of old age, and the teeth were in perfect condition. It died of some acute disease accidentally contracted. I know of another bat of the same species which lived in captivity for more than 15 years, and I have been informed that[60] in the London Zoological Gardens, a fruit bat has lived for 17 years. If these bats were adult when caught, it would be necessary to add something to the known figures.

Although I do not know the exact duration of the life of bats, it is clearly relatively long for mammals no bigger than guinea-pigs. The difference is remarkable if we compare it with the life of sheep, dogs and rabbits, mammals very much larger in size, but possessed of a rich intestinal flora.

The series of facts that I have been discussing strengthens my conviction that the intestinal flora is an extremely important factor in the causation of senility. It must not be supposed, however, that all the known facts can be explained equally easily on this hypothesis. The harm done by microbes cannot always be measured by their abundance in the alimentary canal. In the first place, it must be remembered that some microbes are useful; moreover, microbes, even although their products are very dangerous, may exist in quantities in an organism, and yet do no harm if the organism has the power of resisting bacterial poisons. Thus, for instance, the bacillus of tetanus, which thrives in the alimentary canal, and which can endanger life if the wall of the gut is wounded, does not harm a crocodile or a tortoise, as these animals are extremely resistant to the poison of tetanus. Dr. Favorsky, by experiments at the Pasteur Institute, has shown that the poison of botulism can be absorbed with impunity by some birds, and by tortoises, although death follows if a very small quantity of it be introduced into the alimentary canal of a mammal.

The bodies of man and of higher animals are possessed of a complex mechanism which resists the harmful action of bacteria and their poisons. The various parts of this mechanism may act differently, with the result that there is great variation in the power of resistance. Thus, however abundant microbes may be in the intestine, they may bring little harm to an organism that has a high power of destruction or neutralisation of the toxins, or when these harmful products are unable to pass through the intestinal wall. It is in this way that I explain some exceptions to the general rule, which are exceptions only in appearance. Such a case is that of the nocturnal birds of prey. Although the diurnal birds of prey (eagles, vultures, etc.) have very short cæca, in which the food is never found, owls have very large cæca, which may be as long as 10 cm. (Eagle-Owl, _Bubo maximus_). These long cæca, however, contain debris of the food only in the enlarged terminal portion, and the food masses contain a very small number of microbes. Notwithstanding a great difference in the length of the cæca between the owls and the eagles, these two groups of birds do not differ greatly in longevity. But the difference in the cæca does not imply a corresponding difference in the intestinal flora which appears to be very scanty in both cases.

It is possible that the elephant is a more real exception to the rule. Here is a case of a mammal with an enormous large intestine and a capacious cæcum, and which none the less is capable of surviving for a century. I have had no opportunity of investigating the elephant from this point of view, and have no explanation to suggest.

Monkeys and man differ from most mammals in so far as they possess a long duration of life, although their large intestines are very capacious. I have been unable to get exact information as to the longevity of monkeys, but I understand that these animals live longer than domesticated mammals, such as the ox, sheep, dog, and cat. Anthropoid apes are supposed to be able to reach the age of 50 years. The only other mammal with a longevity similar to that of the elephant is man.

V

DURATION OF HUMAN LIFE

Longevity of man—Theory of Ebstein on the normal
duration of human life—Instances of human
longevity—Circumstances which may explain the long
duration of human life

Man has inherited from his mammalian ancestors his organisation and qualities. His life is notably shorter than that of many reptiles, but longer than that of many birds and most other mammals. None the less he has inherited a capacious large intestine in which a most abundant intestinal flora flourishes.

Gestation and the period of growth are long in the human race, and from the point of view of theoretical considerations, human longevity should be longer than it generally is. Haller, a distinguished Swiss physiologist of the 18th century, thought that man ought to live to 200 years; Buffon was of the opinion that when a man did not die from some accident or disease he would reach 90 or 100 years.

According to Flourens, man takes 20 years to grow and ought to live 5 times 20, that is to say, 100 years.

The actual longevity is much below these figures, which are based on theory. I have shown, moreover, that even if the rule based on the theory of growth can be accepted as generally true, it cannot be applied in every case, as the factors controlling duration of life are very variable.

Statistics show that the highest human mortality occurs in the earliest years of life. In the first year after birth alone, one quarter of the children die. After this period of maximum mortality, the death-rate slowly falls until the age of puberty, and then rises again slowly and continuously. It reaches a second maximum between the ages of 60 and 75, and then slowly falls again to the extreme limit of longevity.

Bodio,[61] an Italian man of science, holds the view that the great mortality of infants is a natural adaptation to prevent too great an increase of the human race. This view, however, cannot be supported, and rational hygiene readily brings about a great diminution in the mortality of children. The cause of mortality is in most cases maladies of the intestinal canal, produced by erroneous diet, and with the advance of civilisation, infant mortality has been very greatly reduced.

I find it impossible to accept the view that the high mortality between the ages of 70 and 75 indicates a natural limit of human life. As a result of investigations into mortality in most of the European countries, Lexis came to the conclusion that the normal duration of human life was not more than 75 years. Dr. Ebstein[62] accepts this statistical result and announces that “we now know the normal limit set by nature to the life of mankind. This limit is at the age of maximum mortality. If man dies before then, his death is premature. Everyone does not reach the normal limit; life ends generally before it, and only in rare cases after it.”

The fact that many men of from 70 to 75 years old are well preserved, both physically and intellectually, makes it impossible to regard that age as the natural limit of human life. Philosophers such as Plato, poets such as Goethe and Victor Hugo, artists such as Michael Angelo, Titian and Franz Hals, produced some of their most important works when they had passed what Lexis and Ebstein regard as the limit of life. Moreover, deaths of people at that age are rarely due to senile debility. In Paris, for instance, in 1902, of cases of deaths between the ages of 70 and 74, only 8·5 per cent. were due to old age.[63] Infectious diseases, such as pneumonia, tuberculosis, diseases of the heart and the kidneys, and cerebral hæmorrhage, caused most of the deaths of these old people. Such cases of death, however, can often be avoided and must be regarded as accidental rather than natural.

Confirmation of the view that the natural limit is not at 70 to 75 years is to be found in the fact that so many men reach a greater age. Centenarians are really not rare. In France, for instance, nearly one hundred and fifty people die every year, after having reached the age of 100 or more. In 1836, in a population of thirty-three millions and a half (33,540,910), there were 146 centenarians, that is to say, one in about 220,000 inhabitants. In some other countries, particularly in Eastern Europe, the number of centenarians is still greater. In Greece, for instance, there is a centenarian for each set of 25,641 living persons, that is to say, nine times as many as in France.[64]

What age can be reached by the human species? Formerly it was supposed that individuals might live for several centuries; to say nothing of Methuselah, whose age of 969 years, mentioned in the Bible, is the result of a mistake in calculation, I may mention Nestor, who, according to Homer, lived for three human ages, that is to say, 300 years, or Dando, the Illyrian, and the King of the Lacedaemon, who were supposed to have reached ages of five or six centuries. These ancient records are, of course, quite incorrect. Much more confidence can be placed in some facts relating to more modern times, according to which the extreme old age reached by man was 185 years. Kentigern, the founder of the Cathedral of Glasgow, known by the name of St. Mungo, died at the age of 185, on Jan. 5th, 600.[65] Another astonishing case of longevity is related from Hungary, where an agriculturist, Pierre Zortay, born in 1539, died in 1724. The Hungarian records of the 18th century contain other cases of death at ages between 147 and 172 years.

The case of Drakenberg is still more authentic; he was born in Norway in 1626 and died in 1772, at the age of 146. He was known as the Old Man of the North. He had been captured by African pirates and was held by them for fifteen years, and was engaged as a sailor for ninety-one years. His romantic history attracted contemporary attention, and the journals of the time (_Gazette de France_, 1764, _Gazette d’Utrecht_, 1767, etc.)[66] contain information regarding him. The well-known instance of Thomas Parr appears to rest on good authority. Parr was a poor Shropshire peasant, who did hard work until he was 130 years old, and who died in London at the age of 152 years and 9 months. The celebrated Harvey examined the body after death and was unable to discover organic disease; even the cartilages of the ribs were not ossified and were elastic as in a young man. The brain, however, was hard and resisting to the touch, as its blood-vessels were thickened and dry. Parr was buried in Westminster Abbey.[67]

It appears, then, that human beings may reach the age of 150, but such cases are certainly extremely rare, and are not known from the records of the last two centuries. I cannot accept without a good deal of reserve the statements as to two persons who died in the beginning of the 19th century at the ages of 142 and 145. On the other hand, cases of duration of life from 100 to 120 years are not very rare.

Extreme longevity is not limited to the white races. According to Prichard,[68] negroes have lived respectively to 115, 160, and 180 years. In the course of the 19th century there have been observed, in Senegal, eight negroes ranging from 100 to 121 years old. M. Chemin[69] saw himself in 1898 at Foundiougne an old man, whom the natives stated to be 108 years of age; although he was in good health, he had been blind for several years. The same author, on the authority of the _New York Herald_ of June 13th, 1895, mentions the case of a coloured woman in North Carolina, who was more than 140 years old, and of a man 125 years old.

Women more frequently become centenarians than men, although the difference is not very great. For instance, in Greece, in 1885, in a population of nearly two millions (1,947,760), there were 278 persons aged from 95 to 110 years, of whom 133 were male and 145 female.

In the seven years, from 1833 to 1839 inclusive, according to Chemin, there were in Paris twenty-six men over the age of 95, and forty-five women. Such facts, and many others, support the general proposition that male mortality is always greater than that of the other sex.

In most cases centenarians are notably healthy and of strong constitution. There are instances, however, of abnormal people having reached a great age. A woman, called Nicoline Marc, died in 1760, at the age of 110. Since she was two years old, her left arm was crippled. Her hand was bent under the arm like a hook. She was a hunch-back, and so bent that she appeared to be no more than four feet high. A Scotch woman, Elspeth Wilson, died at the age of 115 years. She was quite a dwarf, being only a little over two feet high. On the other hand, although they usually have a very short life, giants have been known to reach the age of 100.

Haller, in the eighteenth century, remarked that centenarians often occurred in the same family, as if longevity were a hereditary quality. It is certainly the case that the descendants of centenarians frequently reach extreme age. Thomas Parr, for instance, left a son who died in 1761, at the age of 127 years, having retained his mental faculties until death. In M. Chemin’s list of centenarians, there are eighteen cases of extreme old age having been reached by their relations. As all innate characters can be transmitted, the influence of heredity and longevity must be admitted. At the same time, it is necessary to remember the important influence of the similarity of conditions in the case of parents and children. Many cases of tuberculosis and leprosy, which used to be assigned to heredity, are now known to be due to infection in the same conditions of life, and some of the examples of the attaining of a great age by more than one member of a family may be explained by the influence of surrounding circumstances. Very frequently the husband and wife, although not related by blood, both attain extremely advanced age. I found 22 cases of this kind in M. Chemin’s list; I will give a few of them. A widow, Anne Barak, died at the age of 123, in Moravia; her husband died at the age of 118. In 1896, there was alive in Constantinople, M. Christaki, a retired army doctor of the age of 110; his wife was 95 years old. In 1886, M. et Mme. Gallot, aged respectively 105 years and 4 months, and 105 years and one month, died within two days of each other at Vaugirard, 54, Rue Cambronne. Lejoncourt mentions a South American of 143 years old, whose wife had lived to the age of 117.

It is worth enquiring if there be any relation between longevity and locality. There are some countries in which very many of the natives reach old age. It appears that Eastern Europe (Balkan States, and Russia), although its civilisation is not high, contains many more centenarians than Western Europe. I have already mentioned that Dr. Ornstein had shown the existence of many extremely old people in Greece. M. Chemin states that in Servia, Bulgaria and Roumania there were more than 5,000 centenarians (5,545) living in 1896. “Although these figures appear to be exaggerated,” wrote M. Chemin, “it is undoubtedly the case that the pure and keen air of the Balkans, and the pastoral or agricultural life of the natives, predisposes to old age.” The same author mentions several localities in France, notable for the numbers of very old people. In 1898 in the commune of Sournia (Pyrénées-Orientales) the total population was 600, amongst which there was one woman of 95 years, a man of 94, a woman of 89, two men of 85, two of 84, and two of 83, three women of 82, and two men of 80. At St. Blimont in the Department of the Somme, amongst the 400 inhabitants alive in 1897, there were six men between the ages of 85 and 93 years and one woman in her 101st year.

It cannot be accepted that it is the keen air which lengthens the life, because Switzerland, a mountainous country, is notable for the rarity of centenarians. It is more likely that some circumstance in the mode of living influences longevity.

It has been noticed that most centenarians have been people who were poor, or in humble circumstances, and whose life has been extremely simple. There are instances of rich centenarians, such as Sir Moses Montefiore who died at the age of 101, but such are extremely rare. It may well be said that great riches do not bring a very long life. Poverty generally brings with it sobriety, especially in old age, and it has been often said that most centenarians have lived an extremely sober life. They have not all followed the example of the celebrated Cornaro, who brought himself to subsist on a daily diet of no more than twelve ounces of solid food, and fourteen ounces of wine, and who, although his constitution was weak, lived for about a century. He has left extremely interesting Memoirs, and retained his intelligence until his death on the 26th April, 1566 (Lejoncourt, p. 146).

In M. Chemin’s list I have counted twenty-six centenarians, distinguished by their frugal life. Most of them did not drink wine, and many of them limited themselves to bread, milk and vegetables.

Sobriety is certainly favourable to long life, but it is not necessary, because quite a number of centenarians have drunk freely. Several of those who are catalogued by Chemin, drank wine and spirits even to excess. Catherine Reymond, for instance, who died in 1758 at the age of 107 years, drank much wine, and Politiman, a surgeon who lived from 1685 to 1825, was in the habit, from his twenty-fifth year onwards, of getting drunk every night, after having attended to his practice all day. Gascogne, a butcher of Trie (Hautes-Pyrénées), died in 1767 at the age of 120, and had been accustomed to get drunk twice a week. A most curious example is that of the Irish land-owner Brawn, who lived to the age of 120, and who had an inscription put upon his tombstone that he was always drunk, and when in that condition was so terrible that even death had been afraid of him. Some districts, even, are distinguished at once for the longevity of their inhabitants and for the large local consumption of alcohol. In 1897, village of Chailly in the Côte-d’Or had no less than twenty octogenarians amongst 523 inhabitants. This village is one of the localities in France where most alcohol is consumed, and the old people are very far from being distinguished from their younger fellows by any special sobriety.

In some cases centenarians have been much addicted to the drinking of coffee. The reader will recall Voltaire’s reply when his doctor described the grave harm that comes from abuse of coffee which acts as a real poison. “Well,” said Voltaire, “I have been poisoning myself for nearly 80 years.” There are centenarians who have lived longer than Voltaire, and have drunk still more coffee. Elisabeth Durieux, a native of Savoy, reached the age of 114. Her principal food was coffee, of which she took daily as many as forty small cups. She was jovial and a boon table companion, and used black coffee in quantities that would have surprised an Arab. Her coffee-pot was always on the fire, like the tea-pot in an English cottage (Lejoncourt, p. 84; Chemin, p. 147).

It has been noticed that many centenarians do not smoke, but this like all other traits is not universal. M. Ross, who gained a prize for longevity in 1896 at the age of 102, was an inveterate smoker. In 1897, a widow named Lazennec, died at La Carrière, in Kérinou, Finistère, at the age of 104. She lived in a hovel on charity, and she had smoked a pipe ever since she was quite young.

It is plain that any factor to which long duration of life has been attributed disappears when many cases are examined. Naturally a sound constitution and a simple and sober life are favourable to longevity, but apart from these, there is something unknown which tends to long life. The celebrated physiologist of Bonn, Pflüger,[70] came to the conclusion that the chief condition of longevity is something “intrinsic in the constitution,” something which cannot be defined exactly, and which must be set down to inheritance.

In the present state of knowledge, we cannot denote the chief cause of human longevity, but the proper course will be to seek it out as we would seek out that of animal longevity. As human longevity is often local in its character, and is exhibited by married people who have nothing in common except their mode of life, we may enquire into the intestinal flora and the mechanism by which the organism resists its harmful effect as factors which influence the duration of life. It is reasonable to suppose that in persons living in the same district or under the same roof, the intestinal flora may be similar. The problem can be settled only by a series of laborious researches which have yet to be made. At present I can do no more than bring together a large number of facts regarding the duration of life in man and in animals, with the hope of suggesting the lines for future investigation.