No Sharp Line of between Health and Disease : Part 3

Disease and its Causes
by William Thomas Councilman, M.D.

(Page 4 of 15)

This discussion of injury and repair leads to the question of old age. Old age, as such, should not be discussed in a book on disease, for it is not a disease; it is just as natural to grow old and to die as it is to be born. Disease, however, differs in many respects in the old as compared with the young and renders some discussion of the condition necessary. Changes are constantly taking place in the body with the advance of years, and in the embryo with the advance of days. In every period of life in the child, in the adult, in the middle-aged and in the old we meet with conditions which were not present at earlier periods. There is no definite period at which the changes which we are accustomed to regard as those of old age begin. This is true of both the external appearances of age and the internal changes. One individual may be fully as old, as far as is indicated by the changes of age, at fifty as another at eighty.

With advancing age certain organs of the body atrophy; they become diminished in size, and the microscopic examination shows absence or diminished numbers of the cells which are peculiar to them. The most striking example of this is seen in the sexual glands of females, and, to a less degree, in those of the male. There is a small mass or glandular tissue at the root of the neck, the thymus, which gradually grows from birth and reaches its greatest size at the age of fifteen, when it begins slowly to atrophy and almost disappears at the age of forty. This is the gland which in the calf is known as the sweetbread and is a delicious and valued article of food. The tonsils, which in the child may be so large as to interfere with breathing and swallowing, have almost disappeared in the adult; and there are other such examples.

In age atrophy is a prominent change. It is seen in the loss of the teeth, in the whitening and loss of the hair, in the thinning of the skin so that it more easily wrinkles, in the thinning and weakening of the muscles so that there is not only diminished force of muscular contraction, but weakening of the muscles of support. The back curves from the action of gravity, the strength of the support of the muscles at the back not counteracting the pull of the weight of the abdominal viscera in front. The bones become more porous and more brittle.

The effect of atrophy is also seen in the diminution of all functions, and in loss of weight in individual organs. That the brain shares in the general atrophy is evident both anatomically and in function. Mental activity is more sluggish, impressions are received with more difficulty, their accuracy may be impaired by accompanying changes in the sense organs, and the concepts formed from the impressions may differ from the usual. The slowness of mental action and the diminution in the range of mental activity excited by impressions, and the slowness of expression, may give a false idea of the value of the judgment expressed. The expression changes, the face becomes more impassive because the facial muscles no longer reflect the constant and ever changing impressions which the youthful sense organs convey to a youthful and active brain. That the young should ape the old, should seek to acquire the gravity of demeanor, to restrain the quick impulse, is not of advantage. Loss of weight of the body as a whole is not so apparent, there being a tendency to fat formation owing to the non-use of fat or fat-forming material which is taken into the body. One of the most evident alterations is a general diminution in the fluid of the tissues, to which is chiefly due the lack of plumpness, the wrinkles of age. The facial appearance of age is given to an infant when, in consequence of a long-continued diarrhoea, the tissues become drained of fluid. Every market-man knows that an old animal is not so available for food, the tissues are tougher, more fibrous, not so easily disintegrated by chewing. This is due to a relative increase in the connective tissue which binds all parts together and is represented in the white fibres of meat.

Senile atrophy is complex in its causes and modes of production. The atrophy affects different organs in different degree and shows great variation in situation, in degree and in progress. Atrophic changes of the blood vessels are of great importance, for this affects the circulation on which the nutrition of all tissues depends. While there is undoubted progressive wear of all tissues, this becomes most evident in the case of the blood vessels of the body. It is rare that arteries which can be regarded as in all respects normal are found in individuals over forty, and these changes progress rapidly with advancing age. So striking and constant are these vascular changes that they seem almost in themselves sufficient to explain the senile changes, and this has been frequently expressed in the remark that age is determined not by years, but by the condition of the arteries. Comparative studies show the falsity of this view, for animals which are but little or not at all subject to arterial disease show senile changes of much the same character as those found in man.

There is another condition which must be considered in a study of causes of age. In the ordinary course of life slight injuries are constantly being received and more or less perfectly repaired. An infection which may but slightly affect the ordinary well-being of the individual may produce a considerable damage. Excess or deficiency or improper food, occasional or continued use of alcohol and other poisons may lead to very definite lesions. Repair after injury is rarely perfect, the repaired tissue is more susceptible to injury, and with advancing age there is constant diminution in the ease and perfection of repair. The effect of the sum of all these changes becomes operative: a vicious circle is established in which injury becomes progressively easier to acquire and repair constantly less perfect. There is some adjustment, however, in that the range of activities is diminished, the environment becomes narrower and the organism adapts its life to that environment which makes the least demands upon it.

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. Trees die owing to accidents or because the tree acquires in the course of its growth a mass of tissue in which there is little or no life, and which becomes the prey of parasites. The growing tissue of a tree is comprised in a thin layer below the bark, and the life of this may seemingly be indefinitely prolonged by placing it in a situation in which it escapes the action of accidental injuries and decay, as by grafting on young trees. Where the nature of the dead wood is such that it is immune from parasites and decay, as in the case of the Sequoias, life seems to be indefinitely prolonged. The growing branches of one of these trees, whose age has been estimated with seeming accuracy at six thousand years, are just as fresh and the tree produces its flowers and fruit in the same degree as a youthful brother of one thousand years. Nor does old age supervene in the unicellular organisms. An amoeba assimilates, grows and multiplies just as long as the environment is favorable.

New York, Henry Holt And Company.
London, Williams and Norgate, originally published 1913