LIFE: ITS NATURE, ORIGIN AND MAINTENANCE · AN ADDRESS Shar bey BY E. A. SCHAFER, LL.D., D.Sc., M.D., F.R.S. PROFESSOR OF PHYSIOLOGY IN EDINBURGH LONGMANS, GREEN AND CO. 39 PATERNOSTER ROW, LONDON 1912 325 S53 1912 PREFACE In the following Essay, which formed the Presidential Address to the British Association at its meeting this year in Dundee, I have tried to indicate in clear language the general trend of modern bio-chemical inquiries regarding the nature and origin of living material and the manner in which the life of multicellular organisms, especially that of the higher animals and man, is maintained. I have also stated the conclusions which it appears to me may legitimately be drawn from the result of those inquiries, without ignoring or minimising such difficulties as these conclusions present. There is, it may be admitted, nothing new in the idea that living matter must at some time or another have been formed from lifeless material, for in spite of the dictum omne vivum e vivo, there was certainly a period in the history of the earth when our planet could have supported no kind of life, as we understand the word; there can, therefore, exist no difference of opinion upon this point among scientific thinkers. Nor is it the first time that the possibility of the synthetic production of living substance in the laboratory has been suggested. But only those who are ignorant of the progress which bio-chemistry has made in recent years would be bold enough to affirm that the subject is not more advanced than in the days of Tyndall and of Huxley, who showed the true scientific instinct in affirming a belief in the original formation of life from lifeless material and in hinting at the possibility of its eventual synthesis, although there was then far less foundation upon which to base such an opinion than we of the present day possess. The investigations of Fischer, of Abderhalden, of Hopkins, and of others too numerous to mention, have thrown a flood of light upon the constitution of the materials of which living substance is composed; and, in particular, the epochmaking researches of Kossel into the chemical composition of nuclear substance-which in certain forms may be regarded as the simplest type of living matter, while it is certainly the fons et origo of all active chemical processes within most cells-have shown how much less complex in chemical nature this substance may be than physiologists were a few years ago accustomed to regard it. On this and other grounds it has lately been independently suggested by Professor Minchin that the first living material originally took the form, not of what is commonly 96086 5 termed protoplasm, but of nuclear matter or chromatin: a suggestion which appears by no means improbable. If the honoured names of Charles Darwin, Ernst Häckel, and August Weismann are not found in the following pages, it is because exigencies of space and time rendered it necessary to deal mainly with the more modern developments of this chapter of evolutionary history. For other but not less cogent reasons all metaphysical speculations on the subjects dealt with have been avoided. The study of Natural Knowledge, as the Royal Society still quaintly describes in its title the investigation of the phenomena of Nature, is never properly advanced if mixed up with the 'supernatural' or if metaphysics is appealed to for the explanation of scientific problems which cannot at once be solved by ordinary scientific methods; and it behoves us to eliminate all considerations involving the intervention of supernatural agencies just as much in connection with scientific inquiries into the nature and origin of life as with all other matters which are properly the subject of scientific investigation. This is not materialism, but common sense. The first part of the subject of this Address is dealt with at considerable length and in a strictly scientific spirit by Le Dantec in 'The Nature and Origin of Life'; as well as by Dastre in the book mentioned on the next page. To works such as these the reader is referred for the numerous details which it is impossible to include within the limits of a short Essay. UNIVERSITY, EDINBURGH, LIFE: ITS NATURE, ORIGIN AND MAINTENANCE Definition. EVERYBODY knows, or thinks he knows, what life is; at least, we are all acquainted with its ordinary, obvious manifestations. It would, therefore, seem that it should not be difficult to find an exact definition. The quest has nevertheless baffled the most acute thinkers. Herbert Spencer devoted two chapters of his Principles of Biology' to the discussion of the attempts at definition which had up to that date been proposed, and himself suggested another. But at the end of it all he is constrained to admit that no expression had been found which would embrace all the known manifestations of animate, and at the same time exclude those of admittedly inanimate, objects. The ordinary dictionary definition of life is 'the state of living.' Dastre, following Claude Bernard, defines it as 'the sum total of the phenomena common to all living beings.' Both of these definitions are, however, of the same character as Sidney Smith's definition of an archdeacon as 'a person who performs archidiaconal functions.' I am not myself proposing to take up your time by attempting to grapple with a task which has proved too great for the intellectual giants of philosophy, and I have the less disposition to do so because recent advances in knowledge have suggested the probability that the dividing line between animate and inanimate matter is less sharp than it has hitherto been regarded, so that the difficulty of finding an inclusive definition is correspondingly increased. As a mere word 'life' is interesting in the fact that it is one of those abstract terms which has no direct antithesis; although probably most persons would regard 'death' in that light. A little consideration will show that this is not the case. 'Death' implies the pre-existence of 'life'; there are physiological grounds for regarding death as a phenomenon of life-it is the completion, the last act of life. We cannot speak of a nonliving object as possessing death in the sense that we speak of a living object as possessing life. The adjective' dead' is, it is true, applied in a popular sense antithetically to objects which have never possessed life; as in the proverbial expression' as dead as a door-nail.' But in the strict sense such application is not justifiable, since the use of the terms dead and living implies either in the past or in the present the possession of the recognised properties of living matter. On the other hand, the expressions living and lifeless, animate and inanimate, furnish terms which are un* La vie et la mort, English translation by W. J. Greenstreet, 1911, p. 54. |