The oldest and the most obvious classification of the materials of our environment is into non-living and living; and the accumulation of knowledge in regard to the former is represented in the so-called physical sciences, while that of the latter comprises the content of BIOLOGY, the science of matter in the living state.
Biology, like all science, has as its ultimate object the explanation of its phenomena in terms of the basic concepts matter and energy acting in space and time; but it is needless to say that the realization of this object is not imminent in any department of knowledge, and least of all in the science of living things which exhibit a condition of matter which altogether transcends the classifications of physicist and chemist to-day a condition which expresses in its highest manifestations what we call 'our life.'
Whether the ' riddle of life' will ultimately be solved is a question which every one would like to answer but only the rash would attempt to predict. Suffice it to say that biologists who are on the firing line of progress to-day are directing their attention solely to an attempt to elucidate life phenomena in terms which the chemist and physicist offer. Our present interest, however, is not in discussing the theoretical goal of biology, but in drawing in bold strokes an outline picture of the present-day knowledge of the subject which represents the cumulative results of the application, to problems of life, of the scientific method a method which is not peculiar to science but merely a perfected concentration, of our human resources of observation, experimentation, and reflection. Thus far this has been a most productive method and certainly has given no evidence that its usefulness is being exhausted. To follow any other course would be to abandon the method of science. "In ultimate analysis everything is incomprehensible, and the whole object of science is simply to reduce the fundamental incomprehensibilities to the smallest possible number."
History of Biology
The foundations of the scientific study of living nature were laid by Aristotle and Theophrastus over 2000 years ago. On the basis of collecting, dissecting, classifying, and pondering they reached generalizations, many of which have but recently been put on a firm basis of fact. Indeed these pioneers asked nearly all the broad questions which are fundamental to-day; but from the Greeks until about the fifteenth century there is little to record. There were many additions to the body of knowledge during this long slumber period, but fact and fancy were so amalgamated that the truth was obscured.
The feeling that though Man is of nature, he is still apart, was expressed at the revival of learning in the broad classification of all knowledge as history of nature and history of Man; the former having as its content the record or "history of such facts or effects of nature as have no dependence on Man's will, such as the histories of metals, plants, animals, regions, and the like"; the latter treating of the voluntary actions of men in communities. Thus all record of facts was either natural history or civil history. From this more or less nebulous natural history the present-day sciences of astronomy, physics, chemistry, geology, and biology were thrown off as relatively independent bodies of facts as each gained content, clearness, and individuality. Astronomy, physics or natural philosophy, and chemistry were emancipated first owing to the fact that their material was more readily susceptible to mathematical and experimental treatment, thus leaving the histories of the Earth, animals and plants, or so-called observational sciences, as the residue for natural history. It is in this restricted sense that natural history still lingers.
It remained, however, for Lamarck and Treviranus during the opening years of the nineteenth century to attain a vision of the unity of animal and plant life the unity of ZOOLOGY and BOTANY and to express it in the term biology. But biology is something more than a union of botany and zoology under one name for it endeavors, in addition to describing the characteristics of animals and plants, to unfold the general principles underlying both.
Thus the biologist has as his field the study of living things what they are, what they do, and how they do it. He asks, how this animal or that plant is constructed and how it works and this he attempts to answer.
He would like to ask, why it is so constructed and why it works the way it does but this is beyond the scope of science.
These queries of the biologist reflect the two primary viewpoints from which biological phenomena may be approached: the morphological in which interest centers upon the form and structure of living things, and the physiological in which attention is concentrated upon the functions performed the mechanical and chemical engineering of living machines. Clearly, however, it is impossible to draw a hard and fast distinction between morphology and physiology because in the final analysis structure must be interpreted in terms of function, and vice versa. But again,
The fields of morphology and physiology naturally resolve themselves into special departments of study, depending on the level of analysis of structure or of function which is emphasized. Thus MORPHOLOGY stresses the general form of the animal or plant; ANATOMY, the gross structure of individual parts, or organs; HISTOLOGY, the microscopic structure of organs, or tissues; CYTOLOGY, the component elements of tissues, or cells, and the physical basis of life, or protoplasm. Similarly, PHYSIOLOGY investigates the activities of animals and plants,the functions of organs, the properties of tissues, the phases of cell life, and finally the physico-chemical characteristics of protoplasm. So much for the study of the adult individual animal or plant but this is not all. The origin and development of the individual, and the origin and development of species, ORGANIC EVOLUTION, are other wide fields, sciences in themselves, which must be approached from both the structural and functional aspect if any real advance is to be made toward a comprehensive appreciation of life.
Thus, just as the various physical sciences have expanded and become specialized until they are beyond the grasp of a single man, so biology and its subdivisions, or the BIOLOGICAL SCIENCES, are now distributed among many specialists. Although specialization results in a narrowing and isolating of the fields of study, as deeper levels of investigation have been reached in all the sciences there has been a tendency for the basic phenomena to meet on the common ground of the fundamental sciences, physics and chemistry - for in the last analysis the biologist must assume as a working hypothesis that the properties of protoplasm are the resultant of the properties and interrelationships of the chemical elements which compose it. "In one direction, supported by chemistry and physics, biology becomes bio chemistry and biophysics. In a contrary direction it forms a connection with the psychical sciences which relate to human nature, with psychology and sociology, with ethics and religion."
The Physical Basis of Life
Science never destroys wonder, but only shifts it, higher and deeper. Thomson.
THE old saying that the materials forming the human body change completely every seven years is a tacit recognition that lifeless material, in the form of food, is gradually transformed into similar living matter under the influence of the body. In deed, just as a geyser retains its individuality from moment to moment though it is at no two instances composed of the same molecules of water identically placed, so the living individual is a focus into which materials enter, play a part for a time, and then emerge to become dissipated in the environment. But here the analogy stops. For in the living organism the materials which enter as food, endowed with POTENTIAL energy, are arranged and rearranged until specific molecular aggregates result, which in turn are trans formed into integral parts of the organization of life itself.
However, to live is to work, and to work means expenditure the transformation of the potential into KINETIC energy with the result that materials in relatively simple form and largely or entirely devoid of energy are returned to the realm of the non-living.
Thus we reach a fact of prime importance: so far as we know, living matter is merely ordinary matter which has assumed, for the time being, a peculiar condition in which it displays the remarkable series of phenomena which we recognize as LIFE.
The body of Man in common with that of all animals and plants is composed of living and non-living matter closely associated, though totally distinct. For example, the visible parts of hair and nails, a large part of bone and the liquid part of blood is non-living material. But, the non living is not confined to gross structures, for the dead among the living is still revealed until the resolving power of the microscope fails us.