September 5, 1912] 



NATURE 



19 



prolongation of life. Most of the cells which con- 

 stitute the bodj', after a period of growth and activity, 

 sometimes more, sometimes less prolonged, eventually 

 undergo atrophy and cease to perform satisfactorily 

 the functions which are allotted to them. And when 

 we consider the body as a whole, we find that in every 

 case the life of the aggregate consists of a definite 

 cycle of changes which, after passing through the 

 stages of growth and maturity, always leads to 

 senescence, and finally terminates in death. The onlj' 

 exception is in the reproductive cells, in which the 

 processes of maturation and fertilisation result in 

 rejuvenescence, so that instead of the usual down- 

 ward change towards senescence, the fertilised ovum 

 obtains a new lease of life, which is carried on into 

 the new-formed organism. The latter again itself 

 ultimately forms reproductive cells, and thus the life 

 of the species is continued. It is only in the sense of 

 its propagation in this way from one generation to 

 another that we can speak of the indefinite continu- 

 ance of life : we can only be immortal through our 

 descendants ! 



A~ceragc Duration of Life and Possibility of its 

 Prolongation. 



The individuals of every species of animal appear 

 to have an average duration of existence.-' Some 

 species are known the individuals of which live only 

 for a few hours, whilst others survive for a hundred 

 years. -'^ In man himself the average length of life 

 would probably be greater than the three-score and 

 ten years allotted to him by the Psalmist if we could 

 eliminate the results of disease and accident ; when 

 these results are included it falls far short of that 

 period. If the terms of life given in the purely mytho- 

 logical part of the Old Testament were credible, man 

 would in the early stages of his history have pos- 

 sessed a remarkable power of resisting age and dis- 

 ease. But, although many here present were brought 

 up to believe in their literal veracity, such records 

 are no longer accepted even by the most orthodox of 

 theologians, and the nine hundred odd years vt-ith 

 which Adam and his immediate descendants are 

 credited, culminating in the nine hundred and sixty- 

 nine of Methuselah, have been relegated, with the 

 accounted of Creation and the Deluge, to their proper 

 position in literature. When we come to the Hebrew 

 patriarchs, we notice a considerable diminution to have 

 taken place in what the insurance offices term the 

 "expectation of life." Abraham is described as 

 having lived only to 175 years, Joseph and Joshua to 

 110, Moses to 120; even at that age "his eye was 

 not dim nor his natural force abated." We cannot 

 say that under ideal conditions all these terms are 

 impossible ; indeed, Metchnikoff is disposed to regard 

 them as probable ; for great ages are still occasionallv 

 recorded, although it is doubtful if anv as considerable 

 as these are ever substantiated. That the expecta- 

 tion of life was better then than now would be inferred 

 from the apologetic tone adopted by Jacob when 

 questioned by Pharaoh as to his age : " The days of 

 the years of my pilgrimage are a hundred and thirty 

 years ; few and evil have the days of the years of my 

 life been, and have not attained unto the days of the 

 years of the life of my fathers in the days of their 

 pilgrimage." David, to whom, before the advent of 

 the modern statistician, we owe the idea that seventy 

 years is to be regarded as the normal period of life,^° 



28 This was regarded tjy BufFon as related to the period of growth, hut 

 the ratio is certainly not constant. The subject is discussed by Ray 

 Lankester in an early work: "On Comparative Longevity in Man and 

 Animals," 1870. 



'j^ The approximate regular periods of longevity of different species of 

 animals furnishes a strong .irgument against the theory that the decay of old 

 age is an accidental phenomenon, comparable with disease. 



•1' The expectation of life of a healthy man of fifty is still reckoned at 

 about twenty years. 



NO. 2236, VOL. 90] 



is himself merely stated to have "died in a good 

 old age." The periods recorded for the Kings show 

 a considerable falling-off as compared with the 

 Patriarchs ; but not a few were cut off by violent 

 deaths, and many lived lives which were not ideal. 

 Amongst eminent Greeks and Romans few very long 

 lives are recorded, and the same is true of historical 

 persons in mediaeval and modern history. It is a long 

 life that lasts much beyond eighty ; three such linked 

 together carry us far back into history. Mankind is 

 in this respect more favoured than most mammals, 

 although a few of these surpass the period of man's 

 existence.^' Strange that the brevity of human life 

 should be a favourite theme of preacher and poet 

 when the actual term of his "erring pilgrimage" is 

 greater than that of most of his fellow creatures ! 



The End of Life. 



The modern applications of the principles of pre- 

 ventive medicine and hygiene are no doubt operating 

 to lengthen the average life. But even if the ravages 

 of disease could be altogether eliminated, it is certain 

 that at any rate the fixed cells of our body must 

 eventually grow old and ultimately cease to function ; 

 when this happens to cells which are essential to the 

 life of the organism, general death must result. This 

 will always remain the universal law, from which 

 there is no escape. " All that lives must die, passing 

 through nature to eternity." 



Such natural death unaccelerated by disease — is not 

 death by disease as unnatural as death by accident? — 

 should be a quiet, painless phenomenon, unattended 

 by violent change. As Dastre expresses it, "The 

 need of death should appear at the end of life, just 

 as the need of sleep appears at the end of the day." 

 The change has been led gradually up to by an 

 orderlv succession of phases, and is itself the last 

 manifestation of life. Were we all certain of a quiet 

 passing — were we sure that there would be "no 

 moaning of the bar when we go out to sea " — we 

 could anticipate the coming of death after a ripe old 

 age without apprehension. And if ever the time shall 

 arrive when man will have learned to regard this 

 change as a simple physiological process, as natural 

 as the oncoming of sleep, the approach of the fatal 

 shears will be as generally welcomed as it is now 

 abhorred. Such a day is still distant ; we can scarcely 

 say that its dawning is visible. Let us at least hope 

 that, in the manner depicted by Diirer in his well- 

 known etching, the sunshine which science irradiates 

 may eventually put to flight the melancholy which 

 hovers, bat-like, over the termination of our lives, 

 and which even the anticipation of a future happier 

 existence has not hitherto succeeded in dispersing. 



SECTION A. 



mathematics and physics. 



Opening .Address by Prof. H. L. Callendar, LL.D., 



F.R.S., President of the Section. 



My first duty on taking the chair is to say a few 

 words in commemoration of the distinguished 

 members whom we have lost since the last meeting. 



George Chrystal, Professor of Mathematics in the 

 University of Edinburgh for more than thirty years, 

 officiated as President of this section in the year 1885, 

 and took a prominent part in the advancement of 

 science as secretary of the Roj'al Society of Edinburgh 

 since 1901. Of his brilliant mathematical work and 

 his ability in developing the school at Edinburgh, I 

 am not competent to speak, but I well remember as a 

 student his admirable article on "Electricity and 



•'•i "Hominis aevum csterorum animalium omnium superat prster ad- 

 modum paucoruni." — Francis Bacon, '' Historia vitae et mortis," 1637. 



