Senescence, the Last Half of Life

by G. Stanley Hall

Thus life is a really unbroken continuum from its beginning to its end and we are all connected, as it were, by direct physical participation with the life of our progenitors. Each individual produces a few germ cells that reach the goal of maturity and many somatic cells doomed to death; and in the next generation each repeats the same process. Some flagellate spores, for example, when they divide, lose only the flagellum, which each new individual has to reproduce for itself and this is the rudiment of the corpse that in the higher forms of life becomes indefinitely more bulky and complex; while underneath all this increasing punctuation by death, as it developed, the old plasmal immortality still persists. On the other hand, all forms of fission and agamic budding, so common a method of reproduction in plants and often found in simpler forms of multicellular animal life, such as sponges and coelenterates, are reminiscent of the protozoan fashion.

Thus we see that death came into the world not by reason of sin, as theology teaches, but because of differentiation. As cells acquired the power to produce more and more specialized organs and functions they lost the power to reproduce the entire body and they lost it progressively—almost in exact proportion as their power of multiplication became specific. Thus, as we should expect, we find in the early stages of this differentiation cells that can be influenced toward the old general or the new and more specific powers of reproduction. Yet back of all the fact remains that life itself is essentially perdurable and that we can explain death better than we can explain life. Death is thus not necessary or universal but is derived and is, in a sense, a product of slow development; and we can conceive a stage of evolution in which natural death did not occur at all but was always due to external accidents. Indeed, Weismann goes so far as to say that the difference between the germ and the soma is so great that the latter, with all its fortunes, has little or no influence upon the former; and by his doctrine that acquired traits and qualities are not inheritable he seems to draw a hard and fast line separating the mortal from the immortal parts or organisms. He also devoted the greatest ingenuity in evolving an intricate scheme of biophores, ids, idants, determinants, etc., inherent in germ cells, in order to explain the phenomena of heredity. His studies have had great influence in directing the attention of investigators to the most elementary structures and functions of germ plasm and the remarkable changes within cells that occur in the very earliest stages of embryonic development; while, as we shall see, many of the most recent researches have been directed, since his work was done, to the conditions under which somatic cells in different tissues of the animal body can be made to proliferate and grow, under carefully controlled conditions, more than it was possible for them to do under conditions afforded them while they remained parts of the body in which they were developed.

Here I deem it in point to observe that the adoption in its extreme form of the theory of preformation versus epigenesis, or the assumption that no qualities due to the experiences of the soma can have any influence upon germ plasm or affect heredity, would be to revert to views very like those of the old creationists. From Weismann we may well lay to heart that this influence is very slow and slight in any one or even a large number of generations, suggesting a very long prehistory for the germ plasm of higher organisms. But to hold that nothing in the recent past or the near future of the environment within or without the individual can ever in the least affect innate qualities is to throw ourselves into the arms of a fatalism that more or less blights all the motives of reform and amelioration of conditions or of educational influences in their widest scope. On the contrary, we hold that the ultimate goal of all the improvements of life or mores is to better heredity, that most precious and ancient of all the many forms of values and worths, and that the degree in which they do this is the final criterion of all really worthy endeavor in the world. If the good life of a long series of generations of our ancestors does not in the least tend to make their offspring a little better born and give them some slightly better chance for a worthy, long, and happy life, quite apart from all postnatal, parental, and other influences, the taproot of all motivations for reforming human conditions is cut, and all efforts in this direction become a little falsetto and every generation must start again at the beginning.

Just now we are told that the whole domain of consciousness since civilization began has had little influence upon the deeper and older unconscious elements of human nature but no one among these psychoanalysts has for a moment insisted that it had none. The moral in both cases is simply that we must now make far larger drafts upon the inexhaustible bank of Time and realize that in the one case, body, and in the other, mind, is immeasurably older than we had deemed them to be, that is, that both germ plasm and the unconscious have been very long in the making and come to us charged with potencies innate in the individual but very slowly acquired—in the one case by the ascending orders of animal life from the first and, in the other, by man and his ancestors. We certainly have not yet heard the last word from zoölogy which, while stressing the hereditary factors, for example, and individual longevity, must admit that old age in general is a more or less acquired character. Before we do so, an important correlation, to which I shall advert later, between these investigations and those in the new field of the endocrine glands and the hormones that have such new and marvelous power of speedy and profound influences upon so many parts of and processes that go on in the body, must be made.[168]

One of the chief traits of old age is the loss of germ plasm with its power of perennially regenerating life and this loss leaves the soma to slow degeneration. As germ substance decreases individuality generally increases, sometimes in the form of gross selfishness. As the body becomes cadaverous or corpse-like and the springs of love begin to dry up at their source, secondary sex qualities fade and the sexes again become more alike, as in childhood, and the extremely senile are but the husk or shadow of their former selves. Tenaciously as life is clung to, it is at the same time felt to be less worth saving either here or hereafter, for whoever heard of senile decrepitude wanting to be continued beyond the grave. All ideals of a future life assume a restoration of maturity if not of youth. Doddering, desiccating senility has always been abhorrent to gods and men and I know of no either imaginative or scientific writer who has even attempted to describe the senium as it would be if prolonged to its extremest conceivable term, when each organ and function slowly ceased “altogether and nothing first”—ever shorter in stature, more shriveled and emaciated in form, hairless, the voice shrunk to a whisper, tottering, tremors, and then inability to work, move, or even eat; abatement of all natural functions, the senses slowly becoming extinct, teeth and the power of mastication gone, everything in a stage of progressive involution, increasing paralysis of all receptive or effector processes, offensive perhaps to the very senses of those about, seemingly forgotten for the time by death itself, which the poor victim perhaps longs for but is unable to command the means of attaining, feeling himself useless and a grievous burden, a just living mummy, torpid, neither really sleeping nor waking; and in the end with every natural function sinking synchronously but so gradually that observers could not be sure whether each slow breath or heart beat was really the last or just when the Great Divide had really been crossed where Sleep embraces its brother, Death. Something like this would be the fate of the soma, after it had been abandoned by the germ plasm, if a really natural death occurred, that is, if, by some of the many disharmonies that pervade the body, some organ or part did not break down before the others were worn out and drag them to its own doom, which is what always really occurs in fact.

If we look at the matter from the more psychological and Lamarckian viewpoint, suggested, for example, by the thesis of Hering, that memory is the most fundamental trait of organized matter, a view elaborated by Simon’s theory of mnemes and engrams, all experience is more or less permanently registered on the most vital of living substances, which is “wax to receive and granite to retain,” nerve and brain being the next best organs of registration only acting more specifically; while the most generic resultants of experience attain their ultimate goal of being recorded in the structure or functions of the germ plasm and thus becoming permanent acquisitions of the species or race. On this view the apex of life is reached at that stage of it when the influence of the soma upon the germ plasm is greatest. This, of course, ceases when the latter takes its departure with loss of the power to propagate. Thus of all the stages of life, old age and its fortunes alone can never affect heredity. Individuals who live on do so only by the momentum given by germinal energies transmitted from their parents, and only the old are completely isolated from the main currents of the life of the race. They have already died racially or to the phylum and only await a second or individual death. Thus if any large number of such individuals lived on for many decades, they would be an encumbrance; and so Nature, always intent on the interests of the species and so indifferent to the individual, has to leave them to their fate. They may still alleviate individual conditions but can contribute nothing to racial memories in the above sense. The species has “forgotten them and they are of it forgot.”

* * * * *

Elie Metchnikoff (d. 1916, a.e. 71), a bacteriologist and the successor of Pasteur, who approached the problem of old age from a very different angle and collected many interesting data, was led by his experiments and observations to a unique theory.[169] He first sets forth the disharmonies in the life of animals and especially of man in a way that seems pessimistic; but both his volumes are subtitled “optimistic studies” because he finds hope at the bottom of the Pandora casket.

Old age, he thinks, is not due to loss of the power of somatic cells to divide or reproduce themselves but is “an infectious chronic disease, whether manifested by degeneration or an enfeebling of the nobler elements and by the excessive activity of macrophags,” the latter being large wandering cells represented by the white blood corpuscles and which he holds to be true phagocytes or scavengers, which, instead of protecting as they were meant to do, are very liable to turn on and destroy the higher elements of the body. They are thus like an army raised and sent out to destroy menacing savages that may turn and attack its own city. Old age and death, then, according to Metchnikoff, are not due, as Blütschli thought, to the exhaustion of some kind of vital ferment that protozoa and germ plasm have pre-eminent power to make; nor to the mere accumulation of waste, which the more always tend to dump upon the less vital elements of the body; nor, as Delboeuf conjectured, to the precipitation of the substance of organs, which always tend to revert to their inorganic bases; nor to Roux’s hypothesis that organs are always competing with each other for the available nutritive material, and that as and when there is not enough to satisfy all, those that have to starve drag down the rest; nor to the failure of the initial momentum given at impregnation; nor to the fact that at the senium the body has passed beyond the reach of the influences of sex and its products; but it is due to a very rank and variegated flora or fauna of noxious microbes, and especially to the toxic products they make, which tend to accumulate in the large intestine, making it thus a very cesspool or latrine of the most manifold infections.

Darwinists have stressed the advantages of the large intestine for convenience and the avoidance of the necessity of leaving frequent spoors by which animals might be tracked by their enemies. But many species are without it or have it only in rudimentary form and in man its removal by surgery results in no very serious impairment. We may add, too, that more recently psychoanalysts have described the anus and rectum and their functions as centers of various erotic activities, especially but by no means exclusively in children. Here the waste products of the digestive processes are dumped, awaiting removal, and it has long been known that their undue accumulation caused not only local troubles but general malaise, anxieties, and nervous and mental tensions. Metchnikoff and his pupils showed that very soon after birth noxious bacteria find their way to the large intestine and flourish thereafter in great profusion, especially in constipation, and that no cathartics can be relied on for permanent relief, salutary as medicine has always and everywhere found them for mitigation of many diverse ailments. It is the microbes that find their chief nidus here that are the principal cause of old age and if an antidote to their lethal action could be found Metchnikoff believes life could be very greatly prolonged. He attempts to show that among not only mammals but also birds, the species that have developed the large intestine are less long-lived than those in which it is rudimentary, so that in animals generally its relative size and individual longevity are inversely as each other. Most of the digestive processes are completed before food reaches this terminal part of the long alimentary canal and very little save water can be absorbed through its walls, so that rectal feeding contributes very little, indeed, to the total nutritive needs of the body. But it is here that death finds its chief armamentaria and establishes a receptacle, factory, or laboratory of poisons. Not only are there many microbes that here feed on food residues and occasionally pierce the intestinal walls themselves, but they produce putrefactive products that are still more lethal. The chief of these are phenol and indol, both very complex and due to the breaking down of albuminoids, the chief element in meat, peas, eggs, etc. Young people may for a long time show no trace of the deleterious effects due to the absorption of these toxins, but the slight wear and tear of the tissues they cause is cumulative. They produce in animals old-age effects in kidneys, arteries, liver, lungs, muscles, testes, ovaries, and even in the brain, for senility is due to the action of these bacterial invaders and not to time or to wearing out.