Senescence

“ We have already enough such instances to suggest that senescence normally releases in healthy natures new motivations for the conservation of health and that if these are given their due expression and if all aging men and women came to realize that as the decline of life sets in they must be, more and more, not only their own hygienists but their own physicians, far more might be accomplished in many if not most cases than the world at present suspects. ”

“ In most, the length of life of the individual is determined by that of the shortest-lived essential organ or of the tissue that is least capable of regression and rejuvenation and the development of which, therefore, remains most continuously progressive. In cold-blooded animals where the rate of metabolism is dependent on external temperature, senescence can be reduced by cold, and in certain lower invertebrates by the simple method of underfeeding. ”

“ Happily for her dawning senescence, it is one of the great achievements of our age that she has found a splendid vicarious function in culture and new social, vocational, professional, and political services, so that she can now give to mankind much that is best in her that was once confined to the narrower sphere of domestic life, and be little or none the worse but perhaps the better for it. ”

“ Plenty of food and simple drugs have successfully resisted senility and the train of atrophic degenerations which it involves.
Causes of Senescence.—As for the causes of senescence which have been remedied with such success, they are not exactly known. Calkins thinks that senescence results from the progressive losses to the organism of some substance essential to life. Conjugation or intensive alimentation would act by building up again this necessary compound. ”

“ Of course, in higher animals the progressive features are predominant and development ends in death. But the above generalization275 does not take due account of what occurs in lower organisms, while even in man and other mammals the different tissues do not undergo senescence either alike or synchronously. Some, for example, cells of the epidermis remain relatively young till and after the death of the individual. ”

“ The only practical hope of easement from the hardships of senescence and for the postponement of death now tenable is that now arising faintly and tentatively that, some day, some mitigation of the terrors of old age and death may be found by glandular implantation or perhaps even by the injection of the secretions of certain glands. We know that the germinal glands, and especially their products, have a unique vitality of their own and also that they exert a remarkable and all-pervasive318 influence upon all the organs and functions of the body ”

“ Physiological integration, with its increasing stability of the structural substratum, makes senescence cumulative as we go up the scale of evolution, so that it is ever less balanced or offset by rejuvenation, reproduction, or other regressive changes, as is the case with simple organisms whose life cycle consists merely of brief alternating phases of progression and regression, for the large protozoan cell about to divide is old compared with the two smaller daughter cells formed from it. ”

“ I believe these are the alternating phases of life, and that as we define senescence as an increase and differentiation of the protoplasm, so we must define rejuvenation as an increase of the nuclear material. The alternation of phases is due to the alternation in the proportions of nucleus and protoplasm.
In adults, and even in the old, there are always young cells in reserve, often grouped in certain foci, for example, the marrow of the bones, which can in emergencies come forward, take up the function of growth, regenerate lost tissues or, in lower animals, even lost organs. ”

“ Cells in culture in vitro do not grow old. We see none of the characteristic senescent changes in them.” Thus it may be inferred that when cells show characteristic senescent changes it is because they are “reflecting in their morphology and physiology a consequence of their mutually dependent association in the body as a whole and not any necessary progressive process inherent in themselves. Thus senescence is an attribute of the multicellular body as a whole consequent upon its scheme of morphologic and dynamic organization.” ”

“ Many things meant or not meant to do so, remind us of our age. Friends and perhaps even critics show that they take it into consideration. Shortcomings that date from earlier years are now ascribed to age. We feel, often falsely, that we are observed or even spied upon for signs of its approach, and we are constantly tempted to do or say things to show that it is not yet upon us. Only later comes the stage of vaunting it, proclaiming openly our tale of years and perhaps posing as prodigies of senescence. ”

“ These more marked nodes in the unity of man’s individual existence are: (1) childhood, (2) adolescence from puberty to full nubility, (3) middle life or the prime, when we are at the apex of our aggregate of powers, ranging from twenty-five or thirty to forty or forty-five and comprising thus the fifteen or twenty years now commonly called our best, (4) senescence, which begins in the early forties, or before in woman, and (5) senectitude, the post-climacteric or old age proper. ”

“ The reason that all these essential tissues are not actually immortal in multicellular animals is that the individual parts do not find in the body the conditions necessary for their continued existence, each part being dependent upon other parts. This view differs from Minot’s that there is a specific inherent lethal process going on within the cells themselves that causes senescence. ”

“ Again, we see periodic changes that resemble the age cycle in glands. In the pancreas cell, for example, the loading of the cell is both morphologically and physiologically similar to senescence, and the discharge, to rejuvenescence. In this case the change occurs in individual cells without cell reproduction. Even the cells of the nervous system throughout mature life possess no appreciable capacity for differentiation and regeneration beyond the power to regenerate fibers arising from them. ”

“ If we are allowed to generalize this result, it may be said that senescence, the declining trajectory, the evolution step by step down to death, are not for the cells considered in isolation an inevitable and essentially inherent in the organism, and a rigorous consequence of life itself. ”

“ As a psychologist I am convinced that the psychic states of old people have great significance. Senescence, like adolescence, has its own feelings, thoughts, and wills, as well as its own physiology, and their regimen is important, as well as that of the body. Individual differences here are probably greater than in youth. ”

“ As charity has always been praised as a virtue, it is now becoming also a science, and the peculiar nature and needs of old age are being better understood, although there is yet very much to be done in studying this stage of life which has in the past been so neglected and misunderstood. We are now far more ignorant of senescence than of adolescence, childhood, or middle age, but it is quite as unique, on the whole, and more apart than any of these other periods. ”

“ Whether there is, entirely apart from all conditions affecting nutrition and the effect of injuries which disturb the usual cell activities, an actual senescence of the cells of the body is uncertain. In the presence of the many factors which influence the obvious diminution of cell activity in the old, it is impossible to say whether the loss of cell activity is intrinsic or extrinsic. The life of the plant cell seems to be immortal; it does not grow old. ”

“ In domesticated animals there is hardly any normal old age and they do not seem to know a climacteric. There is a great variation among different races in this period of senescence, which is so peculiar to man. This interval is very brief among savages. But with the beginning of speech all the relations of the individual to his group change. If old animals live on, they do so to themselves and not for the benefit of their kind. ”

“ It is a matter of common observation that in some families senile changes occur much more early than in others, and yet there may be little of degenerative change apparent or probable because of the vigor of the individual. As the gradual steps of growth lead to development, so does the phase of existence called senescence merge insidiously toward the ending called death, through a progressive and insensible diminution in all the organic activities. Death should be regarded as a normal function. Ordinarily it is free from pain and hence should be free from sadness.
Obesity. ”

“ Thus he, too, holds that cancer seems an embryonic reversal and involves no specific changes but is a phenomenon of senescence, a degeneration of cells with an unequal decline in cell functions. Thus races of cells develop that lack the differentiation of undegenerated cells but are still endowed with vegetative and reproductive212 properties. His idea that the degeneration and injury to cells could be responsible for growth, was severely criticised. It was said that any change that meant injury could never be progressive but would lead to diminution of functions. ”

“ It might be said that this period is one of preparation for senescence—as puberty is one of preparation for the cycle of vigorous manhood which normally follows. Senescence, however, does not necessarily mean that beginning with the sixth decade, man is doomed to a profitless and uninteresting final span of life. ”

“ It is not the living matter itself that grows old so much as the framework in which it works--the furnishings of the vital laboratory. There are various processes of rejuvenescence, e.g. rest, repair, change, reorganisation, which work against the inevitable processes of senescence, but sooner or later the victory is with ageing. ”

“ If we had a similar investigation of the old as compared with the young, my own partial studies incline me to believe that this conviction of personal persistence beyond the grave in general loses its force in senescence, as indeed it becomes vital only at adolescence. ”

“ A sagacious and venerable correspondent has suggested to the writer that the time is ripe for some kind of a senescent league of national dimensions which should, of course, establish relations with all existing associations of the old but should slowly develop a somewhat elaborate organization of its own, with committees on finance, on the literature of senescence, including its psychology, physiology and hygiene, etc. ”

“ It becomes dependent on time. It describes a declining trajectory; it experiences evolution, decay, and death. Thus the [Pg 341] fundamental condition of invariable youth and of immortality fails in all metazoa. The vital wastes accumulate in all through the insufficiency or the imperfection of nutritive absorption or of excretion. Life decays; the organism progressively alters, and thus is constituted that state of decrepitude by atrophy or chemical modification which we call senescence, and which ends in death. ”

“ I have found that the cause of this atrophy is the consumption of the muscle fibres by what I call phagocytes, or eating cells, a certain kind of white blood cells.
In the case of certain diseases we find symptoms, which look like precocious senility, due to the poison of the disease. It is no mere analogy to suppose that human senescence is the result of a slow but chronic poisoning of the organism. Such poisons, if not completely destroyed or got rid of, weaken the tissues, the functions of which become altered or enfeebled in which the latter have the advantage. ”

“ The curve has two crests, one in adolescence and the other in senescence.
The chief psychological inference seems to be that the old generally refuse to face squarely and come to357 terms with the death-thought consciously because it is more fatal to them than to the young, but fly to every kind of relief from it by diversion to other things and themes. In age there is often a narrowing of the intellectual horizon to the immediate environment and this itself is opiative. Thus nature alleviates in the old the fear of death, which impends and which they know to be near. ”

“ However it may have been in past geologic ages, it may yet appear that man, on the average, lives longer than any brutes. This he should do if the civilization he has evolved really gives him a more favorable environment than nature and instinct have provided for him. Species, like individuals, very probably have a term of life and become extinct with age, as paleontology shows us not a few have done. But here, too, there is no sufficient basis of fact at present to warrant the generalizations so often met with concerning phyletic immortality or senescence. ”

“ The euthanasia motive is far less pronounced in it.
The second attitude is illustrated by Matthew Arnold146 and by the lugubrious phase of Walt Whitman, both written after decrepitude had begun. Poems written in this spirit arouse the question whether old age is intrinsically pessimistic or perhaps even pathological. Should senescents express or repress the inexorable and progressive limitations and weaknesses senescence brings in its train, or strive to ignore if they cannot be oblivious to them? ”

“ At all events, it seems safe to conclude that the tendency to senescence is pretty general among living organisms, and that this tendency, unless counteracted by a periodic reorganization of the nuclear genes, results inevitably in the deterioration and final extinction of the race. ”