H. W. Conn

“ He had a direct consciousness of his own power to act, and it was natural for him to assume that the activities going on around him were caused by similar powers on the part of some being like himself, only superior to him. Thus he came to fill the unseen universe with gods controlling the forces of nature. The wind was the breath of one god, and the lightning a bolt thrown from the hands of another. ”

“ A small number of the vast host, a score or two of species, unfortunately for us, find their most favourable living place in the human body, and thus become human parasites. By their growth they develop poisons and produce disease. This small class of parasites are then decidedly our enemies. But, taken all together, we must regard the bacteria as friends and allies. Without them we should not have our epidemics, but without them we should not exist. Without them it might be that some individuals would live a little longer, if indeed we could live at all. ”

“ It is a somewhat anomalous fact that a special branch of science, interesting such a large number of people, should be developed around a small group of low plants. The importance of bacteriology is not due to any importance bacteria have as plants or as members of the vegetable kingdom, but solely to their powers of producing profound changes in Nature. There is no one family of plants that begins to compare with them in importance. It is the object of this work to point out briefly how much both of good and ill we owe to the life and growth of these microscopic organisms. ”

“ 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. ”

“ To most people the very word bacteria is almost equivalent to disease, and the thought of swallowing microbes in drinking water or milk is decidedly repugnant and alarming. In the public mind it is only necessary to demonstrate that an article holds bacteria to throw it under condemnation.
We have already seen that bacteria are to be regarded as agents for good, and that from their fundamental relation to plant life they must be looked upon as our friends rather than as our enemies. It is true that there is another side to the story which relates to the parasitic species. ”

“ The Living Body is a Machine.—Reviewing the subject up to this point, what must be our verdict as to our ability to understand the running of the living machine? In the first place, we are justified in regarding the body as a machine, since, so far as concerns its relations to energy, it is simply a piece of mechanism—complicated, indeed, beyond any other machine, but still a machine for changing one kind of energy into another. It receives the energy in the form of chemical composition and converts it into heat, motion, nervous wave motion, etc. ”

“ It is to these powers of producing chemical changes in their food that bacteria owe all their importance in the world. Their power of chemically destroying the food products is in itself of no little importance, but the products which arise as the result of this series of chemical changes are of an importance in the world which we are only just beginning to appreciate. In our attempt to outline the agency which bacteria play in our industries and in natural processes as well, we shall notice that they are sometimes of value simply for their power of producing decomposition ”

“ 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? ”

“ BACTERIA AS AGENTS IN NATURE'S FOOD CYCLE. But the matter by no means ends here. When we come to think of it, it is a matter of considerable surprise that the surface of the earth has been able to continue producing animals and plants for the many millions of years during which life has been in existence. Plants and animals both require food, animals depending wholly upon plants therefor. Plants, however, equally with animals, require food, and although they obtain a considerable portion of their food from the air, yet no inconsiderable part of it is obtained from the soil. ”

“ But a chemical explanation will evidently not suffice for our purpose; for we have absolutely no reason for believing that the phenomena of life can occur as the results of the chemical properties of any compound, however complex. The simplest known form of matter which manifests life is a machine, and the problem of the origin of life must be of the origin of that machine. Are there any forces in nature which are of a sort as to enable us to use them to explain the building of machines? Plants and animals are the only machines which nature has produced. ”

“ Whether other forms of nervous and mental activity can be placed under the same category, or whether these must be regarded as belonging to a realm by themselves and outside of the scope of energy in the physical sense, can not perhaps be yet definitely decided. We can simply say that as yet no one has been able even to conceive how thought can be commensurate with physical energy. The utter unlikeness of thought and wave motion of any kind leads us at present to feel that on the side of mentality the comparison of the body with a machine fails of being complete. ”

“ For a time the multiplying bacteria have an unimpeded course and grow rapidly; but finally their further increase is checked, their vigour impaired, and after this they diminish in numbers and are finally expelled from the body entirely. Of the nature of this new resistance but little is yet known. We notice, in the first place, that commonly after such a recovery the individual has decidedly increased resistance to the disease. This increased resistance may be very lasting, and may be so considerable as to give almost complete immunity from the disease for many years, or for life. ”

“ 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. ”

“ There are, however, some species which cause mankind much trouble by interfering in one way or another with the normal processes of life. These pathogenic bacteria, or disease germs, do not all act alike, but bring about injury to man in a number of different ways. We may recognise two different classes among them, which, however, we shall see are connected by intermediate types. These two classes are, first, the pathogenic bacteria, which are not strictly parasitic but live free in Nature; and, second, those which live as true parasites in the bodies of man or other animals. ”

“ Without it each generation would have to begin anew at the beginning, and nothing could be accomplished. But since this principle brings each individual to the same place where its parents stand, and thus always builds the offspring into a machine like the parent, it makes it possible for the successive generations to advance. Heredity is thus like the power of memory, or better still, like the invention of printing in the development of civilization. ”

“ The history of the rocks has indeed been bound up in the history of life, and no sooner did it appear that the earth's crust has had a readable history than it appeared that living nature had a parallel history. If the present is a key to the past in interpreting geological history, should not the same be true of this history of life? It was inevitable that problems of life should come to the front, and that the study of life from the dynamical standpoint, rather than a statical, should ensue. Modern biology was the child of historical geology. ”

“ But when we turn to the more obscure parts of the nervous phenomena, those which we commonly call mental, we find ourselves obliged to stop abruptly. We may trace the external force to the sensory organ, we may trace this force into a nervous stimulus, and may follow this stimulus to the brain as a wave motion, and therefore as a form of physical energy. But there we must stop. We have no idea of how the nervous impulse is converted into a sensation. The mental side of the sensation appears to stand in a category by itself, and we can not look upon it as a form of energy. ”

“ The marvellous activities of the nucleus, and above all, the fact that the nucleus alone is handed down from one generation to the next in reproduction, all attested to its great importance and to the secondary importance of the rest of the cell.
This was the most extreme position of the cell doctrine. The cell was the unit of living action, and the higher animal or plant simply a colony of such units. An animal was simply an association together for mutual advantage of independent units, just as a city is an association of independent individuals. ”

“ In brief, then, the cell body is a machine for carrying on destructive chemical changes, and liberating from the compounds thus broken to pieces their inclosed energy, which is at once converted into motion or heat or some other form of active energy. This chemical destruction is, however, possible only after the chemical compounds have become a part of the cell. The cell, therefore, possesses a nucleus which has the power of enabling it to assimilate its food—that is, to convert it into its own substance. ”

“ The problem we have set before us is to find out to what extent it is possible to account for vital phenomena by the application of ordinary natural laws and forces, and therefore to find out whether it is necessary to assume that there are forces needed to explain life which are different from those found in other realms of nature, or whether vital forces are all correlated with physical forces. It has been evident at a glance that the living body is a machine. ”

“ Digestion of food is simply a chemical change therein. The food which is taken into the body in the form of sugar, starch, fat or protein, is acted upon by the digestive juices in such a way that its chemical nature is slightly changed. But the changes that thus occur are not peculiar to the living body, since they will take place equally well in the chemist's laboratory. They are simply changes in the molecular structure of the food material, and only such changes as are simple and familiar to the chemist. The forces which effect the change are undoubtedly those of chemical affinity. ”

“ It required now no violent stretch of the imagination to explain the origin of life something as follows: We know that the chemical elements have certain affinities for each other, and will unite with each other under proper conditions. We know that the methods of union and the resulting compounds vary with the conditions under which the union takes place. We know further that the elements carbon, hydrogen, oxygen, and nitrogen have most remarkable properties, and unite to form an almost endless series of remarkable bodies when brought into combination under different conditions. ”

“ That the living body is a machine is a statement that is frequently made without any very accurate idea as to what it means. On the one hand it is made with a belief that a strict comparison can be made between the body and an ordinary, artificial machine, and that living beings are thus reduced to simple mechanisms; on the other hand it is made loosely, without any special thought as to its significance, and certainly with no conception that it reduces life to a mechanism. ”

“ Every animal and plant begins its life as a simple cell, and the growth of the cell into the adult is simply the division of the original cell into parts accompanied by a differentiation of the parts. The fundamental phenomena of growth and reproduction is thus cell division, and if we can comprehend this process in these simple cells we shall certainly have taken a great step toward the explanation of the mechanics of life. ”