Chapter 20

The duration of the life of animals varies within very wide limits. As a general rule, small animals do not live so long as large ones, but there is no absolute relation between size and longevity, since parrots, ravens, and geese live much longer than many mammals, and than some much larger birds. Buffon long ago argued that the total duration of life bore some definite relation to the length of the period of growth, but further inquiry shows that such a relation cannot be established. Nevertheless, there is something intrinsic in each kind of animal which sets a definite limit to the length of years it can attain. The purely physiological conditions which determine this limit leave room for a considerable amount of variation in longevity. Duration of life, therefore, is a character which can be influenced by the environment.

The duration of life in mammals is relatively shorter than in birds, and in the so-called cold-blooded vertebrates. No indication as to the cause of this difference can be found elsewhere than in the organs of digestion. Mammals are the only group of vertebrate animals in which the large intestine is much developed. This part of the alimentary canal is not important, for it fulfils no notable digestive function. On the other hand, it accommodates among the intestinal flora many microbes which damage health by poisoning the body with their products. Among the intestinal flora there are many microbes which are inoffensive, but others are known to have pernicious properties, and auto-intoxication, or self-poisoning, is the cause of the ill-health which may be traced to their activity. It is indubitable 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 the 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 that 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.

When we come to study the duration of human life, it is impossible to accept the view that the high mortality between the ages of seventy and seventy-five indicates a natural limit to human life. The fact that many men from seventy to seventy-five 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 some regard as the limit of life. Moreover, deaths of people at that age are rarely due to senile debility. Centenarians are really not rare. In France, for instance, nearly 150 centenarians die every year, and extreme longevity is not limited to the white races. Women more frequently become centenarians than men--a fact which supports the general proposition that male mortality is always greater than that of the other sex.

It has been noticed that most centenarians have been people who were poor or in humble circumstances, and whose life has been extremely simple. 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 sobriety is certainly favourable to long life.

_II.--The Study of Natural Death_

It is surprising to find how little science really knows about death. By natural death I mean to denote death due to the nature of the organism, and not to disease. We may ask whether natural death really occurs, since death so frequently comes by accident or by disease; and certainly the longevity of many plants is amazing. Such ages as three, four, and five thousand years are attributed to the baobab at Cape Verd, certain cypresses, and the sequoias of California. It is plain that among the lower and higher plants there are cases where natural death does not exist; and, further, so far as I can ascertain, it looks as if poisons produced by their own bodies were the cause of natural death among the higher plants where it does occur.

In the human race cases of what may be called natural death are extremely rare; the death of old people is usually due to infectious disease, particularly pneumonia, or to apoplexy. The close analogy between natural death and sleep supports my view that it is due to an auto-intoxication of the organism, since it is very probable that sleep is due to "poisoning" by the products of organic activity.

Although the duration of the life of man is one of the longest amongst mammals, men find it too short. Ought we to listen to the cry of humanity that life is too short, and that it will be well to prolong it? If the question were merely one of prolonging the life of old people, without modifying old age itself, the answer would be doubtful. It must be understood, however, that the prolongation of life will be associated with the preservation of intelligence and of the power to work. 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. We must use all our endeavors 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.

From time immemorial suggestions have been made for the prolongation of life. Many elixirs have been sought and supposed to have been found, but general hygienic measures have been the most successful in prolonging life and in lessening the ills of old age. That is the teaching of Sir Herman Weber, himself of very great age, who advises general hygienic principles, and especially moderation in all respects. He advises us to avoid alcohol and other stimulants, as well as narcotics and soothing drugs. Certainly the prolongation of life which has come to pass in recent centuries must be attributed to the advance of hygiene; and if hygiene was able to prolong life when little developed, as was the case until recently, we may well believe that with our greater knowledge a much better result will be obtained.

_III.--The Use of Lactic Acid_

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 microbes which inhabit the body. The most important of these belong to the intestinal flora which is abundant and varied. Now the attempt to destroy the intestinal microbes by the use of chemical agents has little chance of success, and the intestine itself may be harmed more than the microbes. If, however, we observe the new-born child we find that, when suckled by its mother, its intestinal microbes are very different and much fewer than if it be fed with cows' milk. I am strongly convinced that it is advantageous to protect ourselves by cooking all kinds of food which, like cows' milk, are exposed to the air. It is well-known that other means--as, for instance, the use of lactic acid--will prevent food outside the body from going bad. Now 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 has been clearly proved that the microbes which produce lactic acid can, and do, control the growth of other microbes within the body, and that the lactic microbe is so much at home in the human body that it is to be found there several weeks after it has been swallowed.

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. The fact that so many races make soured milk and use it copiously is an excellent testimony to its usefulness, and critical inquiry shows that longevity, with few traces of senility, is conspicuous amongst peoples who use sour milk extensively.

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. 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.

_IV.--An Ideal Old Age_

As I have shown in the "Nature of Man," the human constitution as it exists to-day, being the result of a long evolution and containing a large animal element, cannot furnish the basis of rational morality. The conception which has come down from antiquity to modern times, of a harmonious activity of all the organs, is no longer appropriate to mankind. Organs which are in course of atrophy must not be re-awakened, and many natural characters which, perhaps, were useful in the case of animals, must be made to disappear in men.

Human nature which, like the constitutions of other organisms, is subject to evolution, must be modified according to a definite ideal. Just as a gardener or stock-raiser is not content with the existing nature of the plants and animals with which he is occupied, but modifies them to suit his purposes, so also the scientific philosopher must not think of existing human nature as immutable, but must try to modify it for the advantage of mankind. As bread is the chief article in the human food, attempts to improve cereals have been made for a very long time, but in order to obtain results much knowledge is necessary. To modify the nature of plants, it is necessary to understand them well, and it is necessary to have an ideal to be aimed at. In the case of mankind the ideal of human nature, towards which we ought to press, may be formed. In my opinion this ideal is "orthobiosis"--that is to say, the development of human life, so that it passes through a long period of old age in active and vigorous health, leading to a final period in which there shall be present a sense of satiety of life, and a wish for death.

Just as we must study the nature of plants before trying to realise our ideal, so also varied and profound knowledge is the first requisite for the ideal of moral conduct. It is necessary not only to know the structure and functions of the human organism, but to have exact ideas on human life as it is in society. Scientific knowledge is so indispensable for moral conduct that ignorance must be placed among the most immoral acts. A mother who rears her child in defiance of good hygiene, from want of knowledge, is acting immorally towards her offspring, notwithstanding her feeling of sympathy. And this also is true of a government which remains in ignorance of the laws which regulate human life and human society.

If the human race come to adopt the principles of orthobiosis, a considerable change in the qualities of men of different ages will follow. Old age will be postponed so much that men of from sixty to seventy years of age will retain their vigour, and will not require to ask assistance in the fashion now necessary. On the other hand, young men of twenty-one years of age will no longer be thought mature or ready to fulfil functions so difficult as taking a share in public affairs. The view which I set forth in the "Nature of Man" regarding the danger which comes from the present interference of young men in political affairs has since then been confirmed in the most striking fashion.

It is easily intelligible that in the new conditions such modern idols as universal suffrage, public opinion, and the _referendum_, in which the ignorant masses are called on to decide questions which demand varied and profound knowledge, will last no longer than the old idols. The progress of human knowledge will bring about the replacement of such institutions by others, in which applied morality will be controlled by the really competent persons. I permit myself to suppose that in these times scientific training will be much more general than it is just now, and that it will occupy the place which it deserves in education and in life.

Our intelligence informs us that man is capable of much, and, therefore, we hope that he may be able to modify his own nature and transform his disharmonies into harmonies. It is only human will that can attain this ideal.

HUGH MILLER

The Old Red Sandstone

Hugh Miller was born in Cromarty, in the North of Scotland, October 10, 1802. From the time he was seventeen until he was thirty-four, he worked as a common stone-mason, although devoting his leisure hours to independent researches in natural history, for which he formed a taste early in life. He became interested in journalism, and was editor of the Edinburgh "Witness," when, in 1840, he published the contents of the volume issued a year later as "The Old Red Sandstone." The book deals with its author's most distinctive work, namely, finding fossils that tell much of the history of the Lower Old Red Sandstone, and fixing in the geological scale the place to which the larger beds of remains found in the system belong. Besides being a practical and original geologist, Miller had a fine imaginative power, which enabled him to reconstruct the past from its ruinous relics. The fact that he unfortunately set himself the task of combating the theory of evolution, which was fast gaining ground in his day, should not blind us to the high value of his geological experiences. The results of his observations provide some of the most cogent proofs of the theory he disputed. Late in life Miller's mind gave way, and he put an end to his own life on December 24, 1856.

_I.--A Stone-mason's Researches_

My advice to young working men desirous of bettering their circumstances, and adding to the amount of their enjoyment, is to seek happiness in study. Learn to make a right use of your eyes; the commonest things are worth looking at--even stones, weeds, and the most familiar animals. There are none of the intellectual or moral faculties, the exercise of which does not lead to enjoyment; hence it is that happiness bears so little reference to station.

Twenty years ago I made my first acquaintance with a life of labour and restraint. I was but a slim, loose-jointed boy at the time, fond of the pretty intangibilities of romance, and of dreaming when broad awake; and, woful change! I was now going to work in a quarry. I was going to exchange all my day-dreams for the kind of life in which men toil every day that they may be enabled to eat, and eat every day that they may be enabled to toil!

That first day was no very formidable beginning of the course of life I had so much dreaded. To be sure, my hands were a little sore, and I felt nearly as much fatigued as if I had been climbing among the rocks; but I had wrought and been useful, and had yet enjoyed the day fully as much as usual. I was as light of heart next morning as any of my brother-workmen. That night, arising out of my employment, I found I had food enough for thought without once thinking of the unhappiness of a life of labour.

In the course of the day I picked up a nodular mass of blue limestone, and laid it open by a stroke of the hammer. Wonderful to relate, it contained inside a beautifully finished piece of sculpture, one of the volutes, apparently, of an Ionic capital. Was there another such curiosity in the whole world? I broke open a few other nodules of similar appearance, and found that there might be. In one of these there were what seemed to be scales of fishes and the impressions of a few minute bivalves, prettily striated; in the centre of another there was actually a piece of decayed wood.

Of all nature's riddles these seemed to me to be at once the most interesting and the most difficult to expound. I treasured them carefully up, and was told by one of the workmen to whom I showed them that there was a part of the shore, about two miles further to the west, where curiously shaped stones, somewhat like the heads of boarding-pikes, were occasionally picked up, and that in his father's day the country people called them thunderbolts. Our first half-holiday I employed in visiting the place where the thunderbolts had fallen so thickly, and found it a richer scene of wonder than I could have fancied even in my dreams.

My first year of labour came to a close, and I found that the amount of my happiness had not been less than in the last of my boyhood. My knowledge had increased in more than the ratio of former seasons; and as I had acquired the skill of at least the common mechanic, I had fitted myself for independence.

My curiosity, once fully awakened, remained awake, and my opportunities of gratifying it have been tolerably ample. I have been an explorer of caves and ravines, a loiterer along sea-shores, a climber among rocks, a labourer in quarries. My profession was a wandering one. I remember passing direct, on one occasion, from the wild western coast of Ross-shire, where the Old Red Sandstone leans at a high angle against the prevailing quartz of the district, to where, on the southern skirts of Midlothian, the Mountain Limestone rises amid the coal. I have resided one season on a raised beach of the Moray Firth. I have spent the season immediately following amid the ancient granite and contorted schists of the central Highlands. In the north I have laid open by thousands the shells and lignites of the oolite; in the south I have disinterred from their matrices of stone or of shale the huge reds and tree ferns of the carboniferous period.

I advise the stone-mason to acquaint himself with geology. Much of his time must be spent amid the rocks and quarries of widely separated localities, and so, in the course of a few years he may pass over the whole geological scale, and this, too, with opportunities of observation at every stage which can be shared with him by only the gentleman of fortune who devotes his whole time to study. Nay, in some respects, his advantages are superior to those of the amateur, for the man whose employments have to be carried on in the same formation for months, perhaps years, enjoys better opportunities of arriving at just conclusions. There are formations which yield their organisms slowly to the discoverer, and the proofs which establish their place in the geological scale more tardily still. I was acquainted with the Old Red Sandstone of Ross and Cromarty for nearly ten years ere I ascertained that it is richly fossiliferous; I was acquainted with it for nearly ten years more ere I could assign its fossils to their exact place in the scale. Nature is vast and knowledge limited, and no individual need despair of adding to the general fund.

_II.--Bridging Life's Gaps_

"The Old Red Sandstone," says a Scottish geologist in a digest of some recent geological discoveries, "has hitherto been considered as remarkably barren of fossils." Only a few years have gone by since men of no low standing in the science disputed the very existence of this formation--or system, rather, for it contains at least three distinct formations. There are some of our British geologists who still regard it as a sort of debatable tract, entitled to no independent status, a sort of common which should be divided.

It will be found, however, that this hitherto neglected system yields in importance to none of the others, whether we take into account its amazing depth, the great extent to which it is developed both at home and abroad, the interesting links which it furnishes in the geological scale, or the vast period of time which it represents. There are localities in which the depth of the Old Red Sandstone fully equals the elevation of Mount Etna over the level of the sea, and in which it contains three distinct groups of organic remains, the one rising in beautiful progression over the other.

My first statement regarding the system must be much the reverse of the one just quoted, for the fossils are remarkably numerous and in a state of high preservation. I have a hundred solid proofs by which to establish the truth of the assertion within less than a yard of me. Half my closet walls are covered with the peculiar fossils of the Lower Old Red Sandstone; and certainly a stranger assemblage of forms has rarely been grouped together--creatures whose very type is lost, fantastic and uncouth, which puzzle the naturalist to assign them even to their class; boat-like animals, furnished with oars and a rudder; fish, plated over, like the tortoise, above and below, with a strong armour of bone, and furnished with but one solitary rudder-like fin; other fish with the membranes of their fins thickly covered with scales; creatures bristling over with thorns; others glistening in an enamelled coat, as if beautifully japanned; the tail in every instance among the less equivocal shapes formed not equally, as in existing fish, on each side the central vertebral column, but chiefly on the lower side--the column sending out its diminished vertebræ to the extreme termination of the fin. All the forms testify of a remote antiquity. The figures on a Chinese vase or an Egyptian obelisk are scarce more unlike what now exists in nature than are the fossils of the Lower Old Red Sandstone.

Lamarck, on the strength of a few striking facts which prove that to a certain extent the instincts of species may be improved and heightened, has concluded that there is a natural progress from the inferior orders of being towards the superior, and that the offspring of creatures low in the scale may belong to a different and nobler species a few thousand years hence. Never was there a fancy so wild and extravagant. The principle of adaptation still leaves the vegetable a vegetable, and the dog a dog. It is true that it is a law of nature that the chain of being is in some degree a continuous chain, and the various classes of existence shade into each other. All the animal families have their connecting links. Geology abounds with creatures of the intermediate class.

Fishes seem to have been the master existences of two great geological systems, mayhap of three, ere the age of reptiles began. Now, fishes differ very much among themselves, some ranking nearly as low as worms, some nearly as high as reptiles; and we find in the Old Red Sandstone series of links which are wanting in the present creation, and the absence of which occasions a wide gap between the two grand divisions of fishes, the bony and the cartilaginous.