545TH ORDINARY GENERAL MEETING, HELD (BY KIND PERMISSION) IN THE HALL OF THE THE PRESIDENT, THE RT. HON. THE EARL OF HALSBURY, TOOK THE CHAIR. The Minutes of the preceding Meeting were read and signed, and the Secretary announced the election of Professor Theodore Flournoy, of Geneva, as a Life Associate. THE ORIGIN OF LIFE—WHAT DO WE KNOW OF IT? BY PROFESSOR G. SIMS WOODHEAD, M.A., M.D., LL.D., F Fellow of Trinity Hall. ROM the time of the first records of the human race, one subject more than any other appears to have aroused the thought and piqued the curiosity of man-the origin of life. Speculations thereon have ever ever occupied a prominent place and aroused the keenest interest in the human mind, which has busied itself with theories, crude or profound, according to the age, as to the beginnings of the powers which are associated with living matter, and which collectively are spoken of as LIFE. Professor Schäfer, in his interesting and stimulating address delivered before the British Association in September of last year, before giving his definition of life, said, "Everybody knows, or thinks he knows, what life is; at least we are all acquainted with its ordinary manifestations "; but he went on to point out that the most profound and acute thinkers, after devoting themselves to the framing of a definition of life, have been constrained to admit, in the words of Herbert Spencer, that no definition has yet been found "which would embrace all the known manifestations of animate, and at the same time exclude those of inanimate, bodies." It is not my intention to traverse much of the ground covered by Professor Schäfer, as to the non-identity of life with soul, the phenomena indicative of life-movement, assimilation, dis-assimilation-the chemical phenomena accompanying life, the possibility of its synthetic production, and the chemical constitution of living matter; though these, amongst other points, must all be discussed where the question of the origin of life is under consideration. It is evident from a study of the history of this question that, just as the alchemist, in his search for the philosopher's stone and the elixir of life, made observations and came upon facts that constituted much of the foundation of our modern chemistry, so the search for the meaning and origin of life, begun in darkness and continued in shadow, has stimulated most powerfully the development of science and philosophy, and has led men along paths now much more broadly and solidly laid than those "sheep-tracks" on the mountain-side of thought in which they began. The earliest literature with which all are familiar-the Pentateuch-puts forward the hypothesis that life, in the first instance, was of supernatural origin, and then transmitted in perpetuity. In contrast to this, the earlier Greek philosophers had distinct conception of life as having spontaneous origin, accompanied, however, by the idea expressed by Thales in the words:* "All things are full of gods." This idea was more fully developed by Plato and Aristotle as a belief in a "Worldsoul sustaining and moving all that is." Aristotle makes clear his belief that living organisms may arise spontaneously. It must be realised, moreover, that, following the earlier Ionic philosophers, he looked on the universe and the elements from which it was constructed, as being endowed with energy and life, which might be imparted to the organisms developed from and in them. This view was adopted by the poet Lucretius: "The earth has rightly received the name of Mother, since all things are begotten of it, and many living creatures arise out of it, having been generated by the mists and by the warm sun."† During the Middle Ages, the influence of Christianity secured the universal acceptance of the Hebrew view of the creation of life in the first place by supernatural action. But along with * Adam, Religious Teachers of Greece, p. 185. + Given by Macallum from: Linquitur ut merito maternum nomen adepta De Rerum Natura, Lib. V, pp. 793 sqq. NOTE.-I wish here to express my great indebtedness for many valuable suggestions to a paper-“The Origin of Life on the Globe "-contributed to the Transactions of the Canadian Institute, vol. viii, pp. 423-441, by A. B. Macallum, Sc.D., F.R.S., Professor of Biological Chemistry in the University of Toronto. this, there was current the notion that some of the lower forms of life could arise spontaneously. Accurate observation was at a discount in an age that was far from critical. Before the time of Malpighi and Leeuwenhoek, with their lenses and magnifiers, it was impossible to follow the development of those minute organisms in which we can study life in its simplest form; but even had such instruments already existed, they would have been of little use, apart from the more accurate observation and sounder reasoning that followed the Renaissance in Europe. It is exceedingly interesting to follow this question of spontaneous generation, and the various steps by which the arguments advanced in favour of it have been overthrown. Professor Schäfer pointed out that, in the present state of knowledge of the "man in the street," it seems scarcely credible that spontaneous generation, abiogenesis, or the development of living organisms from dead matter, should have assumed such large proportions in the minds of some of the most able of the early scientific investigators. Nothing appears to have been too outrageous to be believed by those who wrote on spontaneous generation. Even as late as the sixteenth century, one able and usually reliable observer, Van Helmont,* stated that it was possible to "create" mice by placing some dirty linen in a receptacle along with a few grains of wheat or a bit of cheese. Later, an Italian, Buonanni, gave a no less startling example of alleged spontaneous generation with elaboration and embellishments of even more fantastic character. Timber rotting in the sea, he said, gave rise to worms, these in turn changed to butterflies, the butterflies ultimately becoming birds. Those who believed in spontaneous generation, however, had not matters all their own way. Francesco Redi,† an Italian poet and physician, was able by a simple experiment, made in 1668, to demonstrate that the worms found in putrefying meat are not, as was generally supposed, the product of spontaneous generation. He simply placed the meat in a wide-mouthed vessel and covered the opening with a piece of gauze. Flies, attracted by the meat, deposited their eggs on the gauze and from the eggs in this position were hatched the worms which, until this experiment was carried out, had been supposed to become organized spontaneously and to receive life in the meat itself. These experiments appeared to settle the point under *Ortus medicinæ . . . ed. ab authoris filio, Amst., 1648. + Experimenta circa generationem insectorum, Amstelodami, 1671. dispute; but in 1683 and subsequent years, Leeuwenhoek* described minute organisms, which we now recognize as bacteria, the origin of which soon became a matter of keen contention. He says: "I saw with very great astonishment, especially in the material mentioned" (from the teeth of an old man who had never used a tooth brush) "that there were many extremely small animals which moved about in a most amusing fashion; the largest of these" (represented by him in an admirable figure)" showed the liveliest and most active motion, moving through rain-water or saliva like a fish of prey darts through the water this form, though few in actual numbers, was met with everywhere. A second form moved round, often in a circle, or in a kind of curve; these were present in greater numbers. The form of a third kind, I could not distinguish clearly; sometimes it appeared oblong, sometimes quite round. They were very tiny, in addition to which they moved forward so rapidly that they tore through one another; they presented an appearance like a swarm of midges and flies buzzing in and out between one another. I had the impression that I saw several thousands in a single drop of water or saliva which was mixed with a small part of the above-named material not larger than a grain of sand, even when nine parts of water or saliva were added to one part of the material taken from the incisor or molar teeth. Further examination of the material showed that out of a large number which were very different in length, all were of the same thickness. Some were curved, some straight, lying irregularly and interlaced." Since, he says, "I had seen minute living animalculæ of the same shape in water, I endeavoured most carefully to observe whether these also were living or not, but I was unable to recognize even the slightest movement as a sign of life." Erasmus Darwin,t speaking of these organisms in 1794, says, perhaps they may be creatures of stagnation or putridity or perhaps no creatures at all Leeuwenhoek's demonstration of the presence of minute organisms in various kinds of putrefying organic matter and even in rainwater was to others an occasion for again calling in spontaneous generation as affording an explanation of the presence of these simple living forms. But he stuck to his views of their function, and to his opposition to the theory of spontaneous generation, which had to wait almost until our time before it was * Omnia Opera, seu Arcana Naturæ ope microscopiorum exactissimorum detecta, Lugd. Bat., 1722. + Zoonomia; or the Laws of Organic Life, London, 1794–1798. men finally crushed by Tyndall and Pasteur. Indeed Leeuwenhoek, "fought steadily against the view that living things are bred from corruption, and showed that weevils (supposed to be bred from wheat as well as in it) are grubs hatched from eggs deposited by insects; and also that the sea mussel was not generated from sand and mud, as Aristotle thought, but from spawn, and he maintained that the same was true of the freshwater mussel . . He showed that eels were not produced from dew, as was then supposed by respectable and learned And many with good reason judge that Nature keeps the same method in invisible creatures that it does in all the sizes of visible, and that even the least as well as the greatest, can be no more made out of corruption than one of the greatest, as a horse."* A fellow countryman of our own, Needham,† took up the cudgels on the other side. With Buffon, he maintained, against his own preconceived notions, however-that spontaneous generation took place continually and universally after death, and sometimes during life, that intestinal worms were formed from the dead matter in the contents of the intestine, certain molecules of the organic matter being set free, becoming re-arranged and entering into a combination that became vitalized. "The eels in flour paste, those of vinegar, all those so-called microscopic animals, are but different shapes taken spontaneously, according to circumstances, by that ever-active matter which only tends to organization." Needham said that dead matter might be heated over a fire, and protected from the air, but that organisms would still be generated in it. An Italian Abbé -Spallanzanit-insisted, however, that there were two weak points in Needham's work. In the first place, he had not exposed the vessels to a sufficient degree of heat to kill the seeds that were inside, and, secondly, as Needham had only closed his vessels with porous cork stoppers, the seeds of living germs could easily have entered the vessels by the pores and so have given birth to animalculæ. Repeating the experiments, Spallanzani used hermetically sealed vases. "I kept them," he says," for an hour in boiling water, and, after having opened them and examined their contents within a reasonable time, I found not the slightest trace of animalculæ, though I had examined with * H. G. Plimmer, F.R.S., J. Roy. Mic. Soc., 1913, p. 133. + Observations upon the Generation, Composition and Decomposition of Animal and Vegetable Substances, London, 1749; Notes s. les Nouvelles Découvertes de Spallanzani, Paris, 1768. Phys. u. Math. Abhandl., Leipzig, 1769; Opuscules de Physique, par Senebier (1776), 1777. |