nation, means—1°, the special manifestations of these organisms, and groups of organisms; or 2°, the causes which produce these manifestations. We are often misunderstood by others, and sometimes vague to ourselves, when we do not bear these two different meanings in view. It was probably some sense of this which made Aristotle distinguish Vitality from Life, as that of the one uniform cause separated from its multiple effects; it was certainly the motive of Fletcher, who thus expressly limits the meanings: "Vitality or Irritability, the property which characterizes organized beings of being acted on by certain powers otherwise than either strictly mechanically or strictly chemically; Life, the sum of the actions of organized beings resulting directly from their vitality so acted on.” * Vitality and Life being thus discriminated as the statical and the dynamical aspects of the organism, we find in relation to the former two radically opposed conceptions: the metaphysiological or extra-organic, and the physiological or intra-organic. The first conceives Vitality to be a Vital Principle, or extra-organic agent, sometimes a soul, spirit, archæus, idea, and sometimes a force, which easily becomes translated into a property. The conception of an entity must be rejected, because it is metempirical and unverifiable, § 34. The conception of a force must be rejected, because it is irreconcilable with any definite idea we have of force. What the term Force signifies in Physics and Chemistry, namely, mass animated by velocity, or directed pressure, which is the activity of the agent, -is precisely that which these vitalists pertinaciously exclude. They assume a force which has nothing in common with mass and velocity; which is not a resultant, but a principle; which * FLETCHER, as quoted by DRYSDALE, Life and the Equivalence of Force, Part II. p. 120. instead of being a directed quantity, is itself autonomous and directive, shaping matter into organization, and endowing it with powers not assignable to matter. If this vital force has any mass at its back, it is a spiritual mass; if it is directed, the direction issues from a "Mind somewhere." Now this conception is purely metempirical. Not only is it inexact to speak of Vitality as a force, it is almost equally inexact to speak of it as a property; since it is a term which includes a variety of properties; and when Fletcher assigns the synonym of Irritability, this at once reveals the inexactness; for beside this property, we must place Assimilation, Evolution, Disintegration, Reproduction, Contractility, and Sensibility, all characteristic properties included in Vitality. 41. Having thus rejected the conceptions of entity, force, and property, we are left in presence of- 1o, the organic conditions as the elements, and 2°, of their synthesis (in the state called organization) as the personified principle. Vital forces, or the vital force, if we adopt the term for brevity's sake, is a symbol of the conditions of existence of organized matter; and since organisms are specially distinguishable from anorganisms by this speciality of their synthesis, and not by any difference in the nature of the elements combined, this state of organization is the "force" or "principle" of which we are in quest. To determine what Life means, we must observe and classify the phenomena presented by living beings. To determine what Vitality-or organization-means, we must observe and classify the processes which go on in organized substances. These will occupy us in the succeeding chapters; here I may so far anticipate as to propose the following definitions: 42. Life is the functional activity of an organism in relation to its medium, as a synthesis of three terms: Structure, Aliment, and Instrument; it is the sum of functions which are the resultants of Vitality; Vitality being the sum of the properties of matter in the state of organization. 43. Vital phenomena are the phenomena manifested in organisms when external agencies disturb their molecular equilibrium; and by organisms when they react on external objects. Thus everything done in an organism, or by an organism, is a vital act, although physical and chemical agencies may form essential components of the act. If I shrink when struck, or if I whip a horse, the blow is in each case physical, but the shrinking and the striking are vital. Every part of a living organism is therefore vital, as pertaining to Life; but no part has this Life when isolated; for Life is the synthesis of all the parts: a federation of the organs when the organism is complex, a federation of the organic substances when the organism is a simple cell. 44. All definitions, although didactically placed at the introduction of a treatise, are properly the final expression of the facts which the treatise has established, and they cannot therefore be fully apprehended until the mind is familiarized with the details they express. Much, therefore, which to the reader may seem unintelligible or questionable in the foregoing definition, must be allowed to pass until he has gone through the chapters which follow. CHAPTER III. ORGANISM, ORGANIZATION, AND ORGANIC SUBSTANCE. 45. THERE is a marked difference between organic and organised substances. The organic are non-living, though capable of living when incorporated in organized tissue (albumen is such a substance); or they may be incapable of living because they have lived, and are products of waste, e. g. urea. The organized substance is a specific combination of organic substances of various kinds, a combination which is organization. Any organized substance is therefore either an independent organism, or part of a more complex organism. Protoplasm, either as a separate organism or as a constituent of a tissue, is organized substance. Organic substances are numerous and specific. They are various combinations of proximate principles familiar to the chemist, which may conveniently be ranged under three classes: The first class of organic substances comprises those composed of principles having what is called a mineral origin; these generally quit the organism unchanged as they entered it. The second class comprises those which are crystallizable, and are formed in the organism, and generally quit it in this state as excretions. The third class comprises the colloids, i. e. substances which are coagulable and not crystallizable, and are formed in and decomposed in the organism, thus furnishing the principles of the second class. All the principles are in a state of solution. Water is the chief vehicle of the materials which enter and the materials which quit the organism; and bodies in solution are solvents of others, so that the water thus acquires new solvent properties. 45 a. Two points must be noted respecting organic substances: they are mostly combinations of higher multiples of the elements; and their combinations are not definite in quantity. Albumen, for example, has (according to one of the many formulas which have been given) an elementary composition of 216 atoms of Carbon, 169 of Hydrogen, 27 of Nitrogen, 3 of Sulphur, and 68 of Oxygen; whereas in its final state, in which it quits the organism as Urea, it is composed of 2 atoms of Carbon, 4 of Hydrogen, 2 of Nitrogen, and 2 of Oxygen, all the Sulphur having disappeared in other combinations. In like manner in the organism Stearin falls from C114, H110 O12, to Oxalic Acid, which is C4, H2, Og. It is obvious that the necessary modifiability of organic substance is due to this multiplicity of its elementary parts and the variety of its molecular structure. * 456. Nor is the indefiniteness of the quantitative composition less important, though seldom adequately appreciated, or even suspected. Robin and Verdeil are the only writers I can remember who have distinctly brought the fact into prominence. That all inorganic substances are definite in composition, every one knows. Quicklime, for example, may be got from marble, limestone, oyster-shells, or chalk; but however produced, it always contains exactly 250 ounces of calcium to 100 ounces of oxygen; just as water is always OH. Not so the preeminently vital substances, those which are coagulable and not crystallizable: no precise formula will express one of these; for the same specific substance is found to vary from time to time, and elementary analyses do not * ROBIN et VERDEIL, Traité de Chimie Anatomique, 1853. |