Part 2

More modern estimates of the duration of human life under ideal conditions of protection against infection have been to the same effect, thus conforming to the estimate of Cornaro,[27] who died at that age, that a hundred years was “the time allowed to man by God and nature.” Metchnikoff,[28] while admitting that there must be variations, considered that man should live more than 100 years, and Luciani fixed the physiological duration of life at 100 years. Ebstein’s (1891) estimate of 70 years as the usual duration of life, which is the age at which the maximum number of deaths occur when the first few years of life are excluded, is different from the ideal duration under the best physiological conditions and corresponds more or less with B. W. Richardson’s rough rule that the individual’s probable age at death can be arrived at by taking the average of the ages of his parents and grandparents; in this procedure the important factor of heredity is taken into account, and the disturbing part played by accidents and infections in modifying the ideal expectation of life is to some extent neutralized by taking the average of the six lives.

Although 100 years may be regarded as the physiological life of man it is rarely reached, and one of several reasons is that the physiological requirements for this apparently exaggerated term of years are very seldom provided. Sir Ray Lankester[29] suggested that just as giants in stature are exceptional variations so centenarians should be regarded in the same light, as giants in years instead of in inches. He meets the obvious objection that whereas the parents of giants are of normal height, longevity and centenarianism appear to run in families, by doubting if the actual quality of potential long life is transmitted and by ascribing family longevity to the inheritance of traditions and habits favourable to long life. In this connexion it should be remembered that many giants are pathological and due to acromegaly, whereas unusual height, over six feet, certainly runs in families; analogy therefore makes it reasonable to believe that length of days, like length in inches, may run in families, although these two approaches to giantism very seldom occur in the same individual.

The authenticity of persons alleged to be of great age rightly excites critical examination, and some of the most famous examples, such as Henry Jenkins (169), Thomas Parr (152¾), Katherine, Countess of Desmond (145), as Sir George Cornewall Lewis and Mr. W. Thom showed, as well as many of the 1712 centenarians in James Easton’s[30] list covering the years A.D. 66 to 1799, cannot be regarded as established.[31] In the same category we must place Petrasch Zorten (1537–1724), whose portrait at the reputed age of 185 was reproduced by Sir John Sinclair.[32] Old people take a natural pride in their age and tend to exaggerate it; according to Mr. G. King[33] the excess in the census returns of persons over 91 and the deficit in those between 85 and 90 years of age could only be explained by the conclusion that the temptation to overstate the age so as to appear among the nonagenarians had not been resisted. The vast majority of centenarians are naturally among the bulk of the population, namely, the poor, among whom natural selection is provided with a correspondingly greater opportunity of finding those “vigorous frames which promise a long life,” and in these circumstances the means of checking the exact age may be less easy than in the case of the well-to-do.

_Sex._--Females are more long-lived than males; the 1911 census for England and Wales shows that after 10 years of age there are more females than males living in all the quinquennial periods, the proportion of females progressively increasing until at the age of 85 and upwards there are 645 females to 355 males in 1000 living at that age group. Among centenarians also the ratio of the sexes is much in favour of that popularly said to be the weaker. Out of the 691 reputed centenarian deaths registered in England and Wales during the 10 years 1910–19 inclusive, 504, or 73 per cent, were females, and 187, or 27 per cent, males. But during the same period in Ireland the disproportion was much less: among the 945 reputed centenarian deaths 545, or 58 per cent, were females, and 400, or 42 per cent, males. It has been said, though without sufficient statistical evidence, that although the female sex is favourable to longevity extreme length of days is attained only by males. The superior longevity of the female sex, in spite of the risks attaching to child-birth, depends on several factors, such as an existence less exposed to accident and infection, a more temperate life, and in addition, so Sir George Humphry argued, on a stronger inherent vitality, for during the first year of life when there is no difference as regards the first two circumstances more boys than girls succumb. The higher male death rate in the first year of life, however, may be partly due to a mechanical cause, namely, the large size of the male infant’s head, as a result of which the numerical superiority of male infants born is reduced by the effects of trauma. Another factor is, perhaps, that old women do not feel so old as old men do, and that therefore auto-suggestion plays a less powerful part with them.

The question must arise as to what is the object of the prolongation of life after the reproductive function has waned as it does in women--the more long-lived of the sexes--about half-way through the physiological term of years. In some lower animals life terminates very shortly after propagation of the species has been effected; but this is not the rule, and the biological meaning of the continuation of the life of individuals that but cumber the ground and may lead a parasitic existence requires explanation, though educational advantages and moral lessons may undeniably be provided by healthy old age with its store of what a Cambridge man, now justly famous, described in his rather rebellious youth as “that greatly over-rated property experience.” It has been suggested by Sir Ray Lankester that the inherent property resulting in longevity may be bound up as a “correlated variation” with some other characteristic useful in the struggle for existence and the perpetuation of the species. An obvious possibility is that the long-lived have a higher fertility rate than average mortals. Hufeland[34] argued that as very old people are nearly always married more than once and generally at a very late period of life “a certain abundance in the power of generation is favourable to longevity.” There are few satisfactory data to determine the converse proposition with which we are now concerned, namely, is longevity accompanied by unusual fertility? As already mentioned, the great majority of centenarians are found among the bulk of the population, namely the poor, who are far more prolific than the well-to-do; but this does not prove much, for the inverse correlation of fertility and good social status is largely artificial and due to voluntary birth control. Among the 824 persons between 80 and 100 years of age analysed by Sir George Humphry[35] in 1889 there were 335 married men and 292 married women, and in each group the average number of children was six, which is somewhat in excess of what is popularly supposed to be the average size of a family; but the question of average fertility is one on which Dr. Major Greenwood warns me that it is difficult to give an unambiguous answer, for it all depends on whether completed or incompleted fertilities are meant; thus in the 1911 census the completed fertilities average 5·8 and the uncompleted 4·2. No value could, he considers, be attached to the general figure obtained by dividing the total number of children by the total number of couples enumerated. Hence Sir George Humphry’s and other statistics are not really comparable. While finding that longevity was equally shared by the single and married women and by those who had children and by those who were barren, Sir George Humphry stated that among those who had children fertility was associated with longevity.

III

ONSET OF OLD AGE

The onset of old age varies in different countries, and, like the development of puberty, is accelerated by the high temperature of tropical countries. There is also considerable variation in families and individuals of the same race and country; thus while one man may be senile at 60 years of age another is vigorous both in mind and body at 80. The inconstancy of onset depends on the various factors that may play a causal part; old age may be a physiological involution, but too often is a pathological product. When the period of reproductive power (maturity) wanes that of old age begins; in women this is marked by the menopause, the age of 45 years being taken as the limit of fertility, but before this even in the late thirties the spectre of fading attractiveness may upset the matron and lead to the irregularities of the “dangerous age.” For man there is no such index, and the change is so insidious that most of us would expostulate at Stanley Hall’s[36] statement that old age in men begins in the early forties and sooner in women, or less than half-way through the physiological lifetime of a hundred years. According to Dante 45 marks the termination of youth, and it seems generally agreed that as a rule--and every one is entitled to consider himself as the exception--

The gay bloom of fifty passes quickly away And people get fat and infirm and all that.

It has from analogy of the female sex been rather fancifully suggested that in man there occurs about the age of fifty a critical period (_climacterium virile_) due to changes in the sex glands (Mendel[37]) or prostate (Rankin[38]); but of this there is no proof. It recalls as a kind of echo the ancient conceptions of the grand climacterics at 49 (a multiple of the number 7), 63 (7 × the magical number 9 of the Arabians), and 81, and the description in 1807 by Professor B. Waterhouse[39] of Cambridge, Mass., who in 1800 introduced Jennerian vaccination into America, of a kind of male moulting between 43 and 50 and a worse one at 63, an idea expanded into the climacteric disease imagined in 1813 by Sir Henry Holland.[40] There is indeed no doubt that after an illness, and the so-called climacteric disease admittedly seldom occurred without some previous factor such as an attack of gout, a common cold, a bout of intemperance, recent marriage, or particularly grief or bereavement, old age may come on apace. In some instances the so-called climacteric disease was perhaps really chronic renal disease, in others merely the prolonged or imperfect convalescence due to some lingering infection after an acute illness, such as influenza; and, as in the latter case recovery may occur, Holland’s contention that recovery was an argument in favour of the existence of this climacteric disease holds good only in distinguishing it from permanent senility, which indeed was the objection that he was concerned to meet. The conception of the climacteric disease is interesting historically only; and it may be agreed that apart from accidents of environment the progress of senescence in healthy men is gradual and uneventful.

So stealthy is the onset of senescence that commonly it is not recognized by its victim and, though he may seldom mention it, every man is firmly convinced that he not only looks but is at least ten years less than the register would tell him. Though unconscious of the change in himself he notes it with perhaps some self-congratulation in his contemporaries. It is only if he tests himself, for example by timing himself for a mile’s walk, that a healthy man of say 70 years has it borne in on him that he is not what he was. The information that he is old may be suddenly conveyed by overhearing the chance remarks of others, by catching a reflection of his bent back in a mirror, by tardy recovery from illness, or the advent of some disability, such as hypertrophy of the prostate or dyspnoea on holiday exertion. Perhaps the commonest warning is a feeling of fatigue. Sir Andrew Clark regarded the onset of old age as the period when a man ceased to adjust himself to his environment; but some persons never are able to do this, and misfits are not necessarily old. Laurentius divided old age beginning at 50 into the three stages of “the green because it is accompanied with prudence, full of experience, and fit to gouerne common weales,” the second at 70 years is “very cold and drie,” and the last, without a specified age incidence, is that of decrepitude corresponding to the famous description in the 12th chapter of Ecclesiastes. A more modern and comforting division is that of Lacassagne[41] of pre-senility, old age beginning at 60 or sometimes 70 in men, and in women 10 to 15 years earlier, advanced old age, and lastly decrepitude. Nascher[42] speaks of a senile climacteric about the latter part of the 7th or 8th decade--the transitional period between old age and decrepitude--corresponding to the changes at puberty and at the menopause.

_Precocious old age_ due to the effects of disease, especially syphilis and acute infections, and to metabolic defects, which permanently damage the cells of the body, has a special interest as it supports Metchnikoff’s pathological view that old age as ordinarily seen is a result of toxic injury (_vide_ p. 82). Hastings Gilford[43] has specially investigated premature senility, and under the title progeria has described a remarkable condition of premature senility combined with, or secondary to, infantilism. This condition was independently described in 1910 by Variot and Pironneau[44] as the senile type of nanism. In such cases it would appear reasonable to ascribe these two opposite conditions to the same toxic or other factor, the infantilism depending more on damage to the ductless glands before development was complete, and the senile changes to direct injury of the cells in the body in general.

IV

FACTORS INFLUENCING LONGEVITY

The determining factors of long life may be broadly divided into those included under heredity, environment, due functional activity, and personal habits. It is impossible to separate these factors into watertight compartments, for a certain amount of overlapping between them is unavoidable.

HEREDITY

The influence of heredity has often been insisted upon and is perhaps the most important factor in longevity. Out of 824 persons between 80 and 100 years of age analysed by Humphry, 406, or 49·4 per cent, came of long-lived families. Numerous striking examples of such families are on record, but a few only need be given. Roy[45] quotes the case of Dr. Iverex, who died in 1700 at the age of 104, his father at 112, his mother 107, and his grandfather 130 years, and gives four other examples of three centenarians in the same family. Another remarkable family group was that of Joseph Retas who died at Tarbes at the age of 118 in 1888, and was the son of a man aged 111 years and had a brother aged 114 years. Two centenarian twin sisters were recorded in a village near Athlone[46]; centenarian sisters and brothers are not so very exceptional. Sir Hermann Weber[47] recorded two families, in one of which the average age of ten children was over 90 years and in the other of eight children nearly 90 years.

A good stock may ensure long life in the face of adverse environment, such as town life and alcoholism; thus Dr. John Brownlee[48] showed statistically that while persons dying at the age of 51 in the average environment would have, had they lived in the country, a mean life of seven years longer, this difference was less at higher ages, and remarks that a person who has the potentiality of living to the age of 80 years has a force of life which is more or less independent of environment. Sir George Savage[49] often noted that of two aged members of the same family one was sober the other intemperate; and a good many centenarians have taken alcohol in quantities that would be too much for ordinary people.

Heredity is not an all-powerful factor, for an individual whose family history is not remarkable for longevity may greatly prolong his life by carefully correcting unfavourable hereditary tendencies. Thus the late Sir Hermann Weber, who lived to the age of 95 as the result of practising the maxims of his _Prolongation of Life_, mentions that his mother died of cardiac failure before she was 60 and his father at 60 from cerebral haemorrhage, and he gives other instances of the same happy result of wise management. Not unfrequently husband and wife both live to an advanced age, no doubt often as the result of favourable environment. A photograph of a married couple both 101 years old appears as the frontispiece of Sir George Humphry’s book on _Old Age_, and must of course be accepted; but the same cannot be said of the frontispiece to volume ii. of Sir John Sinclair’s _Code of Health and Longevity_ (1807), representing the Hungarian husband and wife, aged respectively 172 and 164 years, who had been married 147 years.

It has been suggested that “cell-memory” by providing experience as to the proper way to behave at the different periods of life has a bearing on the coming of old age; Samuel Butler[50] argued that cells without hereditary memory of past existence at, say, 75 years, would become puzzled and so disordered as to die. Parkes Weber[51] has modified this view by assuming a failure of the wish to live on the part of the nerve cells of the brain, a want which might also be hereditary. The possession by the cells of “the will to live” would be an important factor in longevity and should be obtained by individual effort or in other words be an acquired character, though the reverse conditions such as physical mutilations,[52] often spoken of as acquired characters, are known not to be inherited.

In different countries and in different individuals the cells of the body may differ in the rate at which they live; they have, as Sir James Paget[53] said, a different “time-rate”; in some the time-rate is rapid, for example in the natives of hot climates where maturity comes early and old age at a time that seems very premature by our standard; in others the body, sometimes the mind, works slowly, is set at a more leisurely rate and therefore takes longer to run its course. In some persons this appears to be shown by a slow pulse, a characteristic that may also be hereditary.

Of the hereditary factors most concerned in longevity the inherent vitality of the central nervous system is the most essential; physiological death in man and the higher animals is probably due to failure of the cells of the brain, which do not multiply after birth and are less capable of rejuvenescence than those of the other organs. The integrity of the cardio-vascular system is also most important; in Sir William Osler’s[54] words much depends “on the quality of arterial tissue (vital rubber) which the individual has inherited.” According to Sir Clifford Allbutt[55] there are two modes of hereditary transmission of arteriosclerosis, the direct and the indirect; the direct which he calls decrescent or primary, consisting in an original frailty or toxic susceptibility which like other peculiarities may run in families; and the indirect or hyperpietic, a secondary event due not to inherent taint in the arterial walls but to metabolic changes causing high arterial pressure; it is in such families with hereditary high blood pressure that cerebral haemorrhage occurs in one generation after another about the same age (65–70). In examining people the discovery of a blood pressure low for their age often justifies, in the absence of any pathological condition, the suggestion that the family is long-lived. The frequency of cardiac hypertrophy (43 per cent of Councilman’s cases), even though it be a pathological condition, shows that its reserve power is good. Death among the aged very commonly depends on some morbid change in the cardio-vascular system; thus at the Royal Hospital, Chelsea, Majors R. J. C. Thompson and R. E. Todd[56] found that among 169 deaths of pensioners with an average age of 77·2 years the largest number 64, or 38 per cent, were due to this cause; lesions of the respiratory system, pneumonia, and bronchopneumonia, coming next with 41 deaths, or 24 per cent, malignant disease being responsible for 22, or 13 per cent. The nervous and circulatory systems are intimately correlated with each other, disorder or disease of one, particularly of the cardio-vascular system, exerting an evil influence on the other. In a negative manner weakness of the digestive system may favour longevity by preventing the excesses which vigorous individuals may for a time at any rate indulge in with impunity; but as a rule the digestion of the long-lived is good.

The first-born is significantly handicapped, as Karl Pearson[57] has shown, and more subject to tuberculosis, insanity, and criminality. But out of 71 centenarians analysed by Sir George Humphry 17, or 24 per cent, were firstlings, and 24 per cent of 824 persons between 80 and 100 were first-born. It must be remembered that first-born are more numerous than any others, and some of the above were only children. The most frequent position in the family among these 895 old people analysed by Sir George Humphry was the third.

ENVIRONMENT

The influences included under the head of environment are numerous, and this factor cannot be entirely separated from that of heredity, for environment may favour and shape hereditary characteristics. The subject of the harmony and the want of harmony existing between man and his surroundings is so vast that it is possible to touch on a few only of these aspects.