The Story of the Living Machine / A Review of the Conclusions of Modern Biology in Regard / to the Mechanism Which Controls the Phenomena of Living / Activity

by H. W. Conn

This magnificent conception has become the cornerstone of modern science. As soon as conceived it brought at once within its grasp all forms of energy in nature. It is primarily a physical doctrine, and has been developed chiefly in connection with the physical sciences. But it shows at once a possible connection between living and non-living nature. The living organism also exhibits motion and heat, and, if the doctrine of the conservation of energy be true, this energy must be correlated with other forms of energy. Here is a suggestion that the same laws control the living and the non-living world; and a suspicion that if we can find a natural explanation of the burning of a piece of coal and the motion of a locomotive, so, too, we may find a natural explanation of the motion of a living machine.

Evolution—A second conception, whose influence upon-the development of biology was even greater, was the doctrine of evolution. It is true that the doctrine of evolution was no new doctrine with the middle of this century, for it had been conceived somewhat vaguely before. But until historical geology had been formulated, and until the idea of the unity of nature had dawned upon the minds of scientists, the doctrine of evolution had little significance. It made little difference in our philosophy whether the living organisms were regarded as independent creations or as descended from each other, so long as they were looked upon as a distinct realm of nature without connection with the rest of nature's activity. If they are distinct from the rest of nature, and therefore require a distinct origin, it makes little difference whether we looked upon that origin as a single originating point or as thousands of independent creations. But so soon as it appeared that the present condition of the earth's crust was formed by the action of forces still in existence, and so soon as it appeared that the forces outside of living forces, including astronomical, physical and chemical forces, are all correlated with each other as parts of the same store of energy, then the problem of the origin of living things assumed a new meaning. Living things became then a part of nature, and demanded to be included in the same general category. The reign of law, which was claiming that all nature's phenomena are the result of natural rather than supernatural powers, demanded some explanation of the origin of living things. Consequently, when Darwin pointed out a possible way in which living phenomena could thus be included in the realm of natural law, science was ready and anxious to receive his explanation.

Cytology.—A third conception which contributed to the formulation of modern biology was derived from the facts discovered in connection with the organic cell and protoplasm. The significance of these facts we shall notice later, but here we may simply state that these discoveries offered to students simplicity in the place of complexity. The doctrine of cells and protoplasm appeared to offer to biologists no longer the complicated problems which were associated with animals and plants, but the same problems stripped of all side issues and reduced to their lowest terms. This simplifying of the problems proved to be an extraordinary stimulus to the students who were trying to find some way of understanding life.

New Aspects of Biology.—These three conceptions seized hold of the scientific world at periods not very distant from each other, and their influence upon the study of living nature was immediate and extraordinary. Living things now came to be looked upon not simply as objects to be catalogued, but as objects which had a history, and a history which was of interest not merely in itself, but as a part of a general plan. They were no longer studied as stationary, but as moving phases of nature. Animals were no longer looked upon simply as beings now existing, but as the results of the action of past forces and as the foundation of a different series of beings in the future. The present existing animals and plants came to be regarded simply as a step in the long history of the universe. It appeared at once that the study of the present forms of life would offer us a means of interpreting the past and perhaps predicting the future.

In a short time the entire attitude which the student assumed toward living phenomena had changed. Biological science assumed new guises and adopted new methods. Even the problems which it tried to solve were radically changed. Hitherto the attempt had been made to find instances of purpose in nature. The marvellous adaptations of living beings to their conditions had long been felt, and the study of the purposes of these adaptations had inspired many a magnificent conception. But now the scientist lost sight of the purpose in hunting for the cause. Natural law is blind and can have no purpose. To the scientist, filled with the thought of the reign of law, purpose could not exist in nature. Only cause and effect appeal to him. The present phenomena are the result of forces acting in the past, and the scientist's search should be not for the purpose of an adaptation, but for the action of the forces which produced it. To discover the forces and laws which led to the development of the present forms of animals and plants, to explain the method by which these forces of nature have acted to bring about present results, these became the objects of scientific research. It no longer had any meaning to find that a special organ was adapted to its conditions; but it was necessary to find out how it became adapted. The difference in the attitude of these two points of view is world-wide. The former fixes the attention upon the end, the latter upon the means by which the end was attained; the former is what we sometimes call teleological, the latter scientific; the former was the attitude of the study of animals and plants before the middle of this century, the latter the spirit which actuates modern biology.

The Mechanical Nature of Living Organisms.—This new attitude forced many new problems to the front. Foremost among them and fundamental to them all were the questions as to the mechanical nature of living organisms. The law of the correlation of force told that the various forms of energy which appear around us—light, heat, electricity, etc.—are all parts of one common store of energy and convertible into each other. The question whether vital energy is in like manner correlated with other forms of energy was now extremely significant. Living forces had been considered as standing apart from the rest of nature. Vital force, or vitality, had been thought of as something distinct in itself; and that there was any measurable relation between the powers of the living organism and the forces of heat and chemical affinity was of course unthinkable before the formulation of the doctrine of the correlation of forces. But as soon as that doctrine was understood it began to appear at once that, to a certain extent at least, the living body might be compared to a machine whose function is simply to convert one kind of energy into another. A steam engine is fed with fuel. In that fuel is a store of energy deposited there perhaps centuries ago. The rays of the sun, shining on the world in earlier ages, were seized upon by the growing plants and stored away in a potential form in the wood which later became coal. This coal is placed in the furnace of the steam engine and is broken to pieces so that it can no longer hold its store of energy, which is at once liberated in its active form as heat. The engine then takes the energy thus liberated, and as a result of its peculiar mechanism converts it into the motion of its great fly-wheel. With this notion clearly in mind the question forces itself to the front whether the same facts are not true of the living animal organism. It, too, is fed with food containing a store of energy; and should we not regard it, like the steam engine, simply a machine for converting this potential energy into motion, heat, or some other active form? This problem of the correlation of vital and physical forces is inevitably forced upon us with the doctrine of the correlation of forces. Plainly, however, such questions were inconceivable before about the middle of the nineteenth century.

This mechanical conception of living activity was carried even farther. Under the lead of Huxley there arose in the seventh decade of the century a view of life which reduced it to a pure mechanism. The microscope had, at that time, just disclosed the universal presence in living things of that wonderful substance, protoplasm. This material appeared to be a homogeneous substance, and a chemical study showed it to be made of chemical elements united in such a way as to show close relation to albumens. It appeared to be somewhat more complex than ordinary albumen, but it was looked upon as a definite chemical compound, or, perhaps, as a simple mixture of compounds. Chemists had shown that the properties of compounds vary with their composition, and that the more complex the compound the more varied its properties. It was a natural conception, therefore, that protoplasm was a complex chemical compound, and that its vital properties were simply the chemical properties resulting from its composition. Just as water possesses the power of becoming solid at certain temperatures, so protoplasm possesses the power of assimilating food and growing; and, since we do not doubt that the properties of water are the result of its chemical composition, so we may also assume that the vital properties of protoplasm are the result of its chemical composition. It followed from this conclusion that if chemists ever succeeded in manufacturing the chemical compound, protoplasm, it would be alive. Vital phenomena were thus reduced to chemical and mechanical problems.

These ideas arose shortly after the middle of the century, and have dominated the development of biological science up to the present time. It is evident that the aim of biological study must be to test these conceptions and carry them out into details. The chemical and mechanical laws of nature must be applied to vital phenomena in order to see whether they can furnish a satisfactory explanation of life. Are the laws and forces of chemistry sufficient to explain digestion? Are the laws of electricity applicable to an understanding of nervous phenomena? Are physical and chemical forces together sufficient to explain life? Can the animal body be properly regarded as a machine controlled by mechanical laws? Or, on the other hand, are there some phases of life which the forces of chemistry and physics cannot account for? Are there limits to the application of natural law to explain life? Can there be found something connected with living beings which is force but not correlated with the ordinary forms of energy? Is there such a thing as vital energy, or is the so-called vital force simply a name which we have given to the peculiar manifestations of ordinary energy as shown in the substance protoplasm? These are some of the questions that modern biology is trying to answer, and it is the existence of such questions which has made modern biology a new science. Such questions not only did not, but could not, have arisen before the doctrines of the conservation of energy and evolution had made their impression upon the thought of the world.

Significance of the New Biological Problems—It is further evident that the answers to these questions will have a significance reaching beyond the domain of biology proper and affecting the fundamental philosophy of nature. The answer will determine whether or not we can accept in entirety the doctrines of the conservation of energy and evolution. Plainly if it should be found that the energy of animate nature was not correlated with other forms of energy, this would demand either a rejection or a complete modification of our doctrine of the conservation of energy. If an animal can create any energy within itself, or can destroy any energy, we can no longer regard the amount of energy of the universe as constant. Even if that subtile form of force which we call nervous energy should prove to be uncorrelated with other forms of energy, the idea of the conservation of energy must be changed. It is even possible that we must insist that the still more subtile form of force, mental force, must be brought within the scope of this great law in order that it be implicitly accepted. This law has proved itself strictly applicable to the inanimate world, and has then thrust upon us the various questions in regard to vital force, and we must recognize that the real significance of this great law must rest upon the possibility of its application to vital phenomena.

No less intimate is the relation of these problems to the doctrine of evolution. Evolution tries to account for each moment in the history of the world as the result of the conditions of the moment before. Such a theory loses its meaning unless it can be shown that natural forces are sufficient to account for living phenomena. If the supernatural must be brought in here and there to account for living phenomena, then evolution ceases to have much meaning. It is undoubtedly a fact that the rapidly developing ideas along the above mentioned lines of dynamical biology have, been potent factors in bringing about the adoption of evolution. Certain it is that, had it been found that no correlation could be traced between vital and non-vital forces, the doctrine of evolution could not have stood, and even now the special significance which we shall in the end give to evolution will depend upon how we succeed in answering the questions above outlined. The fact is that this problem of the mechanical explanation of vital phenomena forms the capstone of the arch, the sides of which are built of the doctrines of the conservation of energy and the theory of evolution. To the presentation of these problems the following pages will be devoted. The fact that both the doctrine of the conservation of energy and that of evolution are practically everywhere accepted indicates that the mechanical nature of vital forces is regarded as proved. But there are still many questions which are not so easily answered. It will be our purpose in the following discussion to ascertain just what are these problems in dynamical biology and how far they have been answered. Our object will be then in brief to discover to what extent the conception of the living organism as a machine is borne out by the facts which have been collected in the last quarter century, and to learn where, if anywhere, limits have been found to our possibility of applying the forces of chemistry and physics to an explanation of life. In other words, we shall try to see how far we have been able to understand living phenomena in terms of natural force.