Function (biology)

“ We have next to no power of tracing up the genesis of a function considered purely as a function—no opportunity of observing the progressively-increasing quantities of a given action that have arisen in any order of organisms. ”

“ A large number of experiments on the effects produced by changes in the external conditions of life have been made. To this class of investigations belong studies on the regulation of form and function in organisms (Loeb, Child) , the effects produced by altering mechanical conditions of growth, by [Pg 441] changing the chemical environment, etc. There is some internal mechanism in living matter that is influenced by changes in external conditions, and the study of the regulation of the internal processes that produce form and structure have given rise to a variety of interesting problems. ”

“ No matter what we may call this point of vital activity in a cell--whether it be a bioplast, a plastid, a physiological unit, or a granule of "elementary life-stuff"--it simply performs the one single function of life to which it is specifically assigned in the process of "building up" any one identical individual of a species, whether it be a man, an ape, a tree, or a parasitic fungus. ”

“ Physiology is also the first science in which we recognise the influence of habit—the tendency of something to happen again, merely because it has happened before. From physiology, too, we get our clearest notion of what is meant by development, or evolution. The growth of a plant or animal from the first germ is the typical specimen of a phenomenon which rules through the whole course of the history of man and society—increase of function, through expansion and differentiation of structure by internal forces. ”

“ Everywhere the peculiar form of the organism and its structures, internal and external, is directly related to the special physiological functions which the organism or organ has to execute. This intimate connection of structure and function, or of the instrument and the work done by it, is seen in the science of evolution and all its parts. ”

“ The proposed definition of organic life supplies an answer. If organic life be the co-ordination of actions, then an organism may be primarily divided into parts whose actions are co-ordinated, and parts which co-ordinate them—organs which are made to work in concert, and the apparatus which makes them so work—or, in other words, the assimilative, vascular, excretory, and muscular systems on the one hand, and the nervous system on the other. ”

“ In all biological problems it is remarkable how entirely dependent we are upon the philosophy and the methods employed in the exact natural sciences. We transfer all that is there obtainable to the problems of biology. ”

“ Dealing with biology in its general principles, it concerns us only to notice how specially sensitive are the substances of which organisms are built up to the varied influences that act upon organisms. ”

“ THE data of biology are living plants and animals. These are what nature presents. To these we must always go in order to make a beginning at any investigation. Is one interested in ganglionic cells, or germ cells, or liver secretions, or degenerate organs? He must find some kind of animal that has, or produces, or can yield such things. In making a successful quest for "material," it always turns out that a particular individual plant or animal, one or more, furnishes it. ”

“ So that throughout physiological development, as in evolution at large, the multiplication of effects has been a factor constantly at work, and working more actively as the development has advanced. The secondary changes wrought by each primary change, have necessarily become more numerous in proportion as organisms have become more complex. And every increased multiplication of effects, further differentiating the organism and, by consequence, further integrating it, has prepared the way for still higher differentiations and integrations similarly caused. ”

“ We may be sure that a search for the influences determining the maintenance and multiplication of living organisms, cannot be successfully carried out unless we understand what is the peculiar property of a living organism—what is the widest generalization of the phenomena that indicate life. ”

“ It may be said that admitting functional change to be the initiator of variation—granting that the physiological units of an organism long subject to new conditions, will tend to become modified in such way as to cause change of structure in offspring ”

“ Pathology, therefore, is really nothing else than modified physiology. Physiological development is the evolution of organs and the growth of organisms under the impression of natural external conditions; pathological development is the evolution of organs and the growth of organisms under the impression of unnatural external conditions. Adaptation of structure to function—of organisms to surrounding media—is the designed conservative purpose of both kinds of growth. ”

“ Probably not; no great question has ever yet been fully answered—and, although the human organism may be divided, for purposes of study, into numerous sets of apparatus, each having a definite office in the general economy—as the digestive apparatus, the reproductive, the intellectual, etc.—the correlation of all the forces and functions of the body is so intimate and subtile that true philosophy makes no attempt to measure the exact and separate influence of any one force or function upon the rest, or upon the organism as a whole. ”

“ The vital activities taking place in the bodies of higher animals are too complicated and too intricately mixed to admit of clear analysis, and, long ago, physiologists learned that the quest for explanations of living activities lay along the line of investigating them in their most rudimentary expression. The practical recognition of this is seen in our recent text-books upon human physiology, which commonly begin with discussions of the life of these simplest organisms. ”

“ His more immediate effort is to inquire into the nature of the existing organism, to ascertain in what measure the complex phenomena of life as they now appear are capable of resolution into simpler factors or components, and to determine as far as he can what is the relation of these factors to other natural phenomena. It is often practically convenient to consider the organism as presenting two different aspects—a structural or morphological one, and a functional or physiological—and biologists often call themselves accordingly morphologists or physiologists. ”

“ It is the second and perhaps greater task of the biologist to study the organism from the historical point of view, considering it as the product of a continuous process of evolution that has been in operation since life began. ”

“ And yet, though not surprising, this attitude of mind, in face of organic phenomena, is illogical, and is due partly to a misconception of the function of scientific interpretation, partly to influences arising from the course pursued by the historical development of scientific knowledge. The function of biological science is to formulate and to express in generalized terms the related antecedences and sequences which are observed to occur in animals and plants. ”

“ Grouping together the cases first named, in which a particular change in the circumstances of an organism is followed by a particular change in it, and the cases last named, in which the constant actions occurring within an organism imply some constant actions occurring without it; we see that in both, the changes or processes displayed by a living body are specially related to the changes or processes in its environment. And here we have the needful supplement to our conception of Life. ”

“ As displayed in individual organisms, the effects of structures on functions are to be studied, not only in the broad fact that the general kind of life an organism leads is necessitated by the main characters of its organization, but in the more special and less conspicuous fact, that between members of the same species, minor differences of structure lead to minor differences of power to perform certain actions, and of tendencies to perform such actions. ”

“ In order to obtain a Science of Biology, we must analyse the Idea of Life. It has been proved by the biological speculations of past time, that Organic Life cannot rightly be solved into Mechanical or Chemical Forces, or the operation of a Vital Fluid, or of a Soul. ”

“ All other things continuing the same, every additional faculty by which an organism is brought into relation with external objects, as well as every improvement in such faculty, becomes a means of subjecting the organism to a greater number and variety of external stimuli, and to new combinations of external stimuli. ”

“ That which I have here to add, and did not adequately explain in the Principles of Biology, is that the proclivity of units of each order towards the specific arrangement seen in the organism they form, is not to be understood as resulting from their own structures and actions only ”

“ Whatever natures we ascribe to the hypothetical units proper to each kind of organism, we must conclude that from the beginning of embryonic development, they have a proclivity towards the structure of that organism. ”

“ The logical connection between this purely scientific doctrine of disease, or pathology, and ordinary biology, is easily traced. Living matter is characterized by its innate tendency to exhibit a definite series of the morphological and physiological phenomena which constitute organization and life. Given a certain range of conditions, and these phenomena remain the same, within narrow limits, for each kind of living thing. ”

“ And, on the other hand, every individual organism, from the Amœba up to the most complex vertebrate, is, in its structure, its form, its functions, a stupendous marvel of adaptation to its end and of co-ordination of the parts to the whole, and of the whole and its parts to the functions of the organism, the functions of nutrition, self-maintenance, reproduction, maintenance of the species, and so on. ”

“ Conversely, under the reactions of functions on structures in individual organisms, come the facts showing that functions, when fulfilled to their normal extents, maintain integrity of structure in their respective organs; and that within certain limits increases of functions are followed by such structural changes in their respective organs, as enable them to discharge better their extra functions. ”

“ In the lowest organism all parts are competent to perform all functions, and one and the same portion of protoplasm may successfully take on the function of feeding, moving, or reproducing apparatus. In the highest, on the contrary, a great number of parts combine to perform each function, each part doing its allotted share of the work with great accuracy and efficiency, but being useless for any other purpose. ”

“ The conception represents simply the sum of the phenomena exhibited by a living being.
Moreover, the progress which has been made in the solution of the life-question has been gained chiefly by investigation of special functions. But the functions of a vital organism are themselves vital. What, then, is the meaning of "vital" as applied to a function? Fortunately, the answer is not difficult. "Life," says Küss, the distinguished Strasburg physiologist, "is all that can not be explained by chemistry or physics." ”

“ Experimental Biology and General Physiology are one and the same science, in method as well as content, since both aim at explaining life from the physico-chemical constitution of living matter. The series of monographs on Experimental Biology will therefore include the field of traditional General Physiology. ”

“ Finally, we discovered that all these peculiarities are subordinate to the fundamental peculiarity, that vital changes take place in correspondence with external co-existences and sequences, and that the highest Life is reached, when there is some inner relation of actions fitted to meet every outer relation of actions by which the organism can be affected. ”

“ The factors of the second class which we have to keep in view throughout our interpretations, are the formative tendencies of organisms themselves—the proclivities inherited by them from antecedent organisms, and which past processes of evolution have bequeathed. We have seen it to be inferable from various orders of facts (§§ 65, 84, 97–97g) , that organisms are built up of certain highly-complex molecules, which we distinguished as physiological units [or constitutional units as they might otherwise be called] —each kind of organism being built up of units peculiar to itself. ”

“ Just in the same way that the growth of an entire organism is carried on by abstracting from the environment substances like those composing the organism; so the production of each organ within the organism is carried on by abstracting from the substances contained in the organism, those required by this particular organ. ”

“ In like manner Biology is the elaboration of a complete theory of Life, in each and all of its involved manifestations. If different aspects of its phenomena are investigated apart—if one observer busies himself in classing organisms, another in dissecting them, another in ascertaining their chemical compositions, another in studying functions, another in tracing laws of modification; they are {90} all, consciously or un­con­scious­ly, helping to work out a solution of vital phenomena in their entirety, both as displayed by individual organisms and by organisms at large. ”