Physical agent

“ If we may imagine the physico-chemical analysis of the body to be carried through to the very end, may we expect to find at last an unknown something that transcends such analysis and is neither a form of physical energy nor anything given in the physical or chemical configuration of the body? Shall we find anything corresponding to the usual popular conception—which was also along the view of physiologists—that the body is "animated" by a specific "vital principle," or "vital force," a dominating "archæus" that exists only in the realm of organic nature? ”

“ Every function of which we explain the course, the mechanism, or the chemistry, is connected with other functions,—is subservient to them, and they to it; and all together are parts of the general vital system of the animal, ministering to its life, but deriving their activity from the life. Life is not a collection of forces, or polarities, or affinities, such as any of the physical or chemical sciences contemplate ”

“ The physical apparatus of the body are preserved in the aggregate state and form, which are necessary for the performance of their functions by a definite chemical composition of the organs and the fluids which saturate them; and the source of the power required by the living body for its movements is to be sought for in the destruction of the compounds of which it is composed. ”

“ It is impossible to explain in a mechanical way the power which directs the innumerable different chemical and physical processes within the organism, whether they be the bewilderingly purposeful reactions in the individual life of the cell, which seem to point to psychic processes within the plasm, or the riddles of development and of inheritance in particular ”

“ Now, the group of phenomena called vital is more peculiar, more different from other groups than these are from each other, and the science of physiology is a more distinct department than either physics or chemistry, and therefore the form of force, which determines these phenomena, is more distinct and better entitled to a name than any physical or chemical force. ”

“ It has been customary to speak of physics and chemistry as the experimental sciences, but there seem to be equally good reasons why physiology should be taught by experiments also. The processes of respiration, circulation, action of muscles, formation of voice, digestion, and many others admit—nay, demand—illustrative experiments, and the advantages of home-made apparatus are quite as apparent in this field as in the realm of the physical sciences. ”

“ It is necessary to study not only the bodies themselves, but also the laws involved in their formation and decay. We should seek to understand what physical forces are operative in each reaction, and in what quantities. No chemical change can occur unattended by the phenomena of either heat, light, or electricity. ”

“ Anæsthetics, like chloroform, gradually diminish, and finally altogether abolish, electrical response.
Fig. 5.—Simultaneous Record of the Mechanical (M) and (E) Electrical Responses of the Muscle of Frog. (Waller.)
From these observed facts—that living tissue gives response while a tissue that has been killed does not—it is concluded that the phenomenon of response is peculiar to living organisms. [5] The response phenomena that we have been studying are therefore considered as due to some unknown, super-physical ‘vital’ force and are thus relegated to a region beyond physical inquiry. ”

“ Molecular forces, therefore, are the agencies which determine the particular state of the body in its physical relations, considering it as an independent whole—or, as it is termed in modern mechanics, as an independent conservative system—while the molar forces determine the physical relations of the body to other bodies which, together with it, are integrant parts of a greater whole, i. ”

“ This leads us on to the consideration of the essential characteristics of the living organism, consisting as it does of some of the most abundant and most widely distributed of these material elements, and being always subject to the general laws of matter. The best authorities in physiology are quoted, as to the extreme complexity of the chemical compounds which constitute the physical basis for the manifestation of life; as to their great instability; their wonderful mobility combined with permanence of form and structure ”

“ If the properties of such a system of bodies are found to correspond to those of gases, an important physical analogy will be established, which may lead to more accurate knowledge of the properties of matter. ”

“ It seeks for the first and best explanation of organic beings in the mere mechanical effects of their surroundings. The physical forces which act upon them from outside—the water or the air that bathes them—the impacts of ethereal undulations in the form of light, the vibrations of matter in contact with them in the form of heat—these are conceived of as the agencies principally concerned. ”

“ The only consistent attitude is that of the physicist who assumes that the reac­tions and structures of animals are consequences of the chemical and physical forces, which no more serve a purpose than those forces responsible for the solar systems. ”

“ If we strictly examine the immense series of living bodies, we shall see the vital properties gradually augmenting in number and energy, from the lowest of plants to the first of animals, man; we shall see the lowest plants obedient to vital and physical properties; all plants are governed only by these, which, in them, consist of insensible contractility and organic sensibility; the lowest animals begin to add sensible organic contractility to these properties, afterwards animal sensibility and contractility. ”

“ There has always been a fierce resistance to the attempt to explain vital and sentient phenomena on mechanical, or even physical principles, but still the question has incessantly recurred, How far is the organism mechanically interpretable? And while the progress of Biology has shown more and more the machine-like adjustment of the several parts of which the organism is composed, it has also shown more and more the intervention of conditions not mechanically interpretable.362 We shall have to consider the question, therefore, under two forms. ”

“ But to avoid undue suspension of the argument, I content myself with saying that when the respective effects of gravitation, heat, light, &c., are studied, as well as the respective effects, physical and chemical, of the matters forming the media, water and air, it will be found that while more or less operative on all bodies, each modifies organic bodies to an extent immensely greater than the extent to which it modifies inorganic bodies. ”

“ It is in its wider bearings, its bearings beyond strict specialties in science, that the influence of the theory of physical-chemical adequacy in the treatment of life phenomena is most unfortunate. Only when regarded from this larger standpoint does its withering effect on the scientific spirit and method generally, and on man's attitude toward nature, become apparent. ”

“ Among biologists who confess themselves supporters of the mechanical theory, there are some who expressly reject explanations in terms of [pg 258] chemical and physical principles, and emphasise, more energetically than others, that these can only give rise to vital phenomena and complex processes of movement, on the basis of a most delicately differentiated structure and architecture of the living substance in its minute details, and from the egg onwards. ”

“ The one class comprises all the agencies in the External Medium which appreciably affect the organism; the other class all the changes in the organism which appreciably disturb the equilibrium of any organ. Although the pressure of the atmosphere, for example, unquestionably affects the organism, and determines organic processes, it is not reckoned as a stimulus unless the effect become appreciable under sudden variations of the pressure. ”

“ Behold a man with his wonderful body, and still more wonderful mind; try to think of him as being fathered and mothered by the mere mechanical and chemical forces that we see at work in the rocks and soil underfoot, begotten by chemical affinity or the solar energy working as molecular physic, and mothered by the warmth and moisture, by osmosis and the colloid state—and all through the chance clashings and groupings of the irrational physical forces. ”

“ The force which the plant stores up is undeniably physical; must not the force which the animal sets free by its conversion, be intimately correlated to it?
But approaching our question still more closely, let us, in illustration of the vital forces of the animal economy, choose three forms of its manifestation in which to seek for the evidences of correlation; these shall be heat, evolved within the body; muscular energy or motion; and lastly, nervous energy, or that form of force which, on the one hand, stimulates a muscle to contract, and on the other, appears in forms called mental. ”

“ But although similar alterations in the medium notoriously influence the organism, yet, because a great many variations in external conditions are unaccompanied by appreciable changes in the organism, there are biologists who regard this as a proof of Life being independent of physical and chemical laws ”

“ In the study of the first problem we have reached the general conclusion that the secondary phenomena of life are readily explained by the application of physical and chemical forces acting in the living machine. These secondary phenomena include such processes as the digestion and absorption of food, circulation, respiration, excretion, bodily motion, etc. ”

“ We do not deny the presence of phenomena in organisms which belong to physical and chemical agencies, but we assert that organisms have other phenomena besides these, dependent on conditions not present in physical and chemical phenomena. ”

“ The physiological chemist has at length discovered that the human body, and every organ of that body consists of a certain number of chemical elements, which appear in different parts in different aggregations. These aggregations, however, repeat themselves in the various parts or organs. ”

“ An account of the modes in which the force generated in organisms by chemical change, is transformed into other forces, and made to work the various organs that carry on the functions of Life, comes under the head of Organic Physics. ”

“ It is not, however, necessary to suppose that the agent of which we are treating particularly requires a chemical action to develop it, or the action of the electric force. Experiments have proved that it is developed in every form of material action—that even the substances of the earth, without sensible alteration, exert this force. To this agent the sensitive nerve centres are extremely susceptible. ”

“ For it has always been the task of this line of investigation to extend the sphere within which physical and chemical laws can be validly applied in interpreting vital processes, and the results reached along this line will always be so numerous and important that even on psychological grounds the mechanical point of view has the best chance for the future. ”

“ Are we to ascribe to the operation of a fluid or fluids, and if so, in what manner, the facts of heat, magnetism, electricity, galvanism? What are the forces by which the elements of chemical compounds are held together? What are the forces, of a higher order, as we cannot help believing, by which the course of vital action in organized bodies is kept up? In these and other cases, we have extensive departments of science; but we are as yet unable to trace the effects to their causes; and our science, so far as it is positive and certain, consists entirely of the laws of phenomena. ”

“ We clearly conceive the manner how, and the conditions by which, motility, this most prominent vital manifestation, constitutes an inherent property of the living substance. Do we as yet comprehend in the same way the intimate modes of activity which constitute the properties appertaining to inorganic substances? Is any kind of those peculiar motions which form the scientific essence of the various forces of inorganic Nature so strictly and deeply intelligible as has now become that specific motion which forms the scientific essence of the force of life? ”

“ To some extent, the parts of every body are changed in their arrangement by any incident mechanical force. But in organic bodies, and especially in animal bodies, the changes of arrangement produced by mechanical forces are usually conspicuous. ”

“ But I must go still further, and affirm that in the eye of science the animal body is just as much the product of molecular force as the chalk and the ear of corn, or as the crystal of salt or sugar. Many of the parts of the body are obviously mechanical. Take the human heart, for example, with its system of valves, or take the exquisite mechanism of the eye or hand. ”

“ When by chemical or physical experiment we obtain con­fi­gur­a­tions similar, for instance, to the phenomena of nuclear division, or conformations similar to a pattern of hexagonal cells, or a group of vesicles which resemble some particular tissue or cell-aggregate, we indeed prove what it is the main object of this book to illustrate, namely, that the physical forces are capable of producing particular organic forms. ”

“ And thus, under a logical analysis, which must be admitted to be legitimate, it may be maintained that a body or chemical element resolves itself into a system of centres of force balancing each other at certain distances, and thus rendering the whole molecule or mass extended, as body is known to be. ”