incidental observations he makes, I by no means accept his system. Those general doctrines in which I agree with him, are those which he holds in common with sundry other thinkers. With all those general doctrines which are distinctive of his philosophy, I disagree — with all those at least that I have definite knowledge of; for beyond the first half of his " Course of Positive Philosophy," I know his opinions only by hearsay.
COlUlKSro^^DHXCE BETVVEKN LIFE AND ITS CIRCUMSTANCES. 75 on ill II plant pre-suppose a surrounding medium containing at least carbonic acid and water, together with a due supply of light and a certain temperature. Within the leaves carbon is being assimilated and oxygen given off; without them, is the gas from which the carbon is abstracted, and the imponderable agents that aid the abstraction. Be the nature of the process what it may, it is clear that there are external elements prone to undergo special re-arrangements under special conditions. It is clear that the plant in sunshine presents these conditions and so effects these re-arrangements. And thus it is clear that the changes which constitute the plant's life, are in correspondence with co-existences in its environment.
If, again, we ask respecting the lowest protozoon, how it lives; the answer is, that while on the one hand its substance is ever undergoing oxidation, it is on the other hand ever absorbing nutriment; and that it may continue to exist, the assimilation must keep pace with, or exceed, the oxidation. If further we ask under what circumstances these combined changes are possible; there is the obvious reply, that the medium in which the protozoon is placed, must contain oxygen and food — oxygen in such quantity as to produce some disintegration; food in such quantity as to permit that disintegration to be made good. In other words — the two antagonistic processes taking place internally, imply the presence externally of materials having affinities that can give rise to these processes.
Leaving those lowest animal forms revealed by the microscope, which simply take in through their surfaces the nutriment and oxygenated fluids coming in contact with them, we pass to those somewhat higher forms which have their tissues partially specialized into assimilative and respiratory. In these we see a correspondence between certain actions in the digestive sac, and the properties of certain surrounding bodies. That a creature of this order may continue to live, it is necessary not only that there be masses of substance in. tlie environment capable of transformation into its own tissue; but that the introduction of these masses into its stomach, shall be followed by the secretion of a solvent fluid that will reduce them to a fit state for absorption. Special outer properties must be met by special inner properties.
When, from the process by which food is digested, we turn to the processes by which it is seized, we perceive the same general truth. The stinging and contractile power of a polype's tentacle, correspond to the sensitiveness and strength of the creatures serving it for prey. Unless that external chanofe which brino:s one of these creatures in contact with the tentacle, were quickly followed by those internal changes which result in the coiling and drawing up of the tentacle, the polype would die of inanition. The fundamental processes of integration and disintegration within it, would get out of correspondence with the agencies and processes without it; and the life would cease.
Similarly, it may be shown that when the creature becomes so large that its tissue cannot be eificiently supplied with nutriment by mere absorption through its limiting membranes, or duly oxygenated by contact with the fluid that bathes its surface, there arises a necessity for a circulatory system by which nutriment. and ox3^gen maybe distributed throughout the mass; and the functions of this system, being subsidiary to the two primary functions, form links in the correspondence between internal and external actions. The like is obviously true of all those subordinate functions, secretory and excretory, that facilitate oxidation and assimilation — functions in which we may trace, both cotemporaneous changes answering to co-existences in the environment, and successive changes answering to those changes of composition, of temperature, of light, of moisture, of pressure, which the environment undergoes.
Ascending from the visceral actions to the muscular and nervous actions, we find the correspondence displayed in a manner still more obvious. Every act of locomotion implies CORJIESPONDENCE BETWEEN LIFE AND ITS C1KCUMSTA^'CES. 77 the expenditure of certain internal mechanical forces, adapted in amounts and directions to balance or out- balance certain external ones. The recognition of an object is impossible without a harmony between the changes constituting perception, and particular properties co-existing in the environment. Escape from enemies supposes motions within the organism, related in kind and rapidity to motions without it. Destruction of prey requires a particular combination of subjective actions, fitted in degree and succession to overcome a group of objective ones. And so with those countless automatic processes exemplified in works on animal instinct.
In the highest order of vital changes, the same fact is equally manifest. The empirical generalization that guides the farmer in his rotation of crops, serves to bring his actions into concord with certain of the actions going on in plants and soil. The rational deductions of the educated navisrator who calculates his position at sea, constitute a series of mental acts by which, his proceedings are conformed to surrounding circumstances. Alike in the simplest inferences of the child, and the most complex ones of the man of science, we find a correspondence between simultaneous and successive changes in the organism, and co-existences and sequences in its environment.
§ 29. This general formula, which thus includes the lowest vegetal processes as well as the highest manifestations of human intelligence, will perhaps call forth some criticisms which it is desirable here to meet.
It may be thought that there are still a few inorganic actions included in the definition; as for example that displayed by the mis-named storm -glass. The feathery crystallization which, on a certain change of temperature, takes place in the solution contained by this instrument, and which afterwards dissolves to reappear in new forms under new conditions, may be held to present simultaneous and successive changes that are to some extent heterogeneous, that occur with" some defiiiiteness of combination, and, above all, occur in correspondence with external changes. In this case vegetal life is simulated to a considerable extent; but it is merely simulated.
The relation between the phenomena occurring in the stormglass and in the atmosphere respectively, is really not a correspondence at all, in the proper sense of the word. Outside there is a certain change; inside there is a change of atomic arrangement. Outside there is another certain change; inside there is another change of atomic arrangement. But subtle as is the dependence of each internal ujDon each external change, the connexion between them does not, in the abstract, differ from the connexion between the motion of a straw and the motion of the wind that disturbs it. In either case a change produces a change, and there it ends. The alteration wrought by some environing agency on an inanimate object, does not tend to induce in it a secondary alteration, that anticipates some secondary alteration in the environment. But in every living body there is a tendency towards secondary alterations of this nature; and it is in their production that the correspondence consists. The difference may be best expressed by symbols. Let A be a change in the environment; and B some resulting change in an inorganic mass. Then A having produced B, the action ceases. Though the change A in the environment, is followed by some consequent change a in it; no parallel sequence in the inorganic mass simultaneously generates in it some change h that has reference to the change a. But if we take a living body of the requisite organization, and let the change A impress on it some change C; then, while in the environment A is occasioning a, in the living body C will be occasioning c: of which a and c will show a certain concord in time, place, or intensity. And while it is in the continuous production of suoh concords or correspondences that Life consists, it is by the continuous production of them that Life is maintained.
The further criticism that may be expected, concerns cer- CORRESPONDENCE BETWEEN LIFE AND ITS CIRCUMSTANCES. 70 tain verbal imperfections in the definition, which it seems impossible to avoid. It may bo fairly urged that the word correspondence will not include, without straining, the various relations to be expressed by it. It may be asked: — How can the continuous processes of assimilation and respiration, correspond with the co-existence of food and oxygon in the environment? or again: — How can the act of secreting some defensive fluid, correspond with some external danger which may never occur? or again: — How can the dijnamical phenomena constituting perception, correspond with the statical phenomena of the solid body perceived? The only reply to these questions, is, that we have no word sufficiently general to comprehend all forms of this relation between the organism and its medium, and yet sufficiently specific to convey an adequate idea of the relation; and that the word correspondence seems the least objectionable. The fact to be expressed in all cases, is, that certain changes, continuous or discontinuous, in the organism, are connected after such a manner that, in their amounts, or variations, or periods of occurrence, or modes of succession, they have a reference to external actions, constant or serial, actual or potential — a reference such that a definite relation among any members of the one group, implies a definite relation among certain members of the other group; and the word correspondence appears the best fitted to express this fact.
§ 30. The presentation of the phenomena under this general form, suggests how our definition of Life may be reduced to its most abstract shape; and perhaps its best shape. By regarding the respective elements of the definition as relations, we avoid both the circumlocution and the verbal inaccuracy; and that we may so regard them with propriety is obvious. If a creature's rate of assimilation is increased in consequence of a decrease of temperature in the environment; it is that the relation between the food consumed and heat produced, is so re-adjusted by multiplying both its members, that the altered relation in the surrounding medium between the quantity of heat absorbed from, and radiated to, bodies of a given temperature, is counterbalanced. If a sound or a scent wafted to it on the breeze, prompts the stag to dart away from the deer-stalker; it is that there exists in its neighbourhood a relation between a certain sensible property and certain actions dangerous to the stag, while in its organism there exists an adapted relation between the impression this sensible property produces, and the actions by which danger is escaped. If inquiry has led the chemist to a law, enabling him to tell how much of any one element will combine with so much of another; it is that there has been established in him specific mental relations, which accord with specific chemical relations in the things around. Seeing, then, that in all cases we may consider the external phenomena as simply in relation, and the internal phenomena also as simply in relation; the broadest and most complete definition of Life will be — The continuous adjustment of internal relations to external relations* While it is simpler, this modified formula has the further advantage of being somewhat more comprehensive. To say that it includes not only those definite combinations of simultaneous and successive changes in an organism, which correspond to co-existences and sequences in the environment, but also those structural arrangements which enable the organism to adapt its actions to actions in the environment, may perhaps be going too far; for though these structural arrangements present internal relations adjusted to external relations, yet the contitiuous adjustme^it of relations can scarcely be held to include a fixed adjustment already made. Clearly, Life, which is made up of dynamical phenomena, cannot be defined in terms that shall at the same time define the apparatus manifesting it, which presents only statical phenomena. But while this antithesis serves to remind us that the fundamental distinction between the organism and * In further elucidatiou of this general doctrine, see First Principles, § 25.
^' CORRESPONDENCE BETWEEN LIFE AND ITS CIRCUMSTANCES. 81 its actions, is as wide as that between Matter and Motion, it at the same time draws attention to the fact, that if the structural arrangements of the adult are not properly included in the definition, yet the developmental processes by which those arrangements were established, are included. For that process of evolution during which the organs of the embr3^o are fitted to their prospective functions, is from beginning to end the gradual or continuous adjustment of internal relations to external relations. Moreover, those structural modifications of the adult organism, which, under change of climate, change of occupation, change of food, slowly bring about some re- arrangement in the organic balance, must similarly be regarded as continuous adjustments of internal relations to external relations. So that not only does the definition, as thus expressed, comprehend all those activities, bodily and mental, which constitute our ordinary idea of Life; but it also comprehends, both those processes of development by which the organism is brought into general fitness for these activities, and those after-processes of adaptation by which it is specially fitted to its special activities.
Nevertheless, superior as it is in simplicity and comprehensiveness, so abstract a formula as this is scarcely fitted for our present purpose. Reserving its terms for such use as occasion may dictate, it will be best commonly to employ its more concrete equivalent — to consider the internal relations as " definite combinations of simultaneous and successive changes; " the external relations as " co- existences and sequences; " and the connexion between them as a " correspondence."
CHAPTER YI.
THE DEGREE OF LIFE VARIES AS THE DEGREE OF CORRESPONDENCE.
§ 31. Already it has been shown respecting each other qualification included in the foregoing definition, that the life is high in proportion as that qualification is well fulfilled; and it is now to be remarked, that the same thing is especially true respecting this last qualification — the correspondence between internal and external relations. It is manifest a priori, that since changes in the physical state of the environment, as also those mechanical actions and those variations of available food which occur in it, are liable to stop the processes going on in the organism; and since the adaptive changes in the organism have the efiects of directly or indirectly counterbalancing these changes in the environment; it follows that the life of the organism will be short or long, low or high, according to the extent to which changes in the environment are met by corresponding changes in the organism. Allowing a margin for perturbations, the life will continue only while the correspondence continues; the completeness of the life will be proportionate to the completeness of the correspondence; and the life will be perfect only when the correspondence is perfect. Not to dwell in general statements, however, let us contemplate this truth under its concrete aspects.
§ 32. In life of the lowest order, we find that only the THE MKK VARIES AS THE CORRESPONDENCE. 83 most prevalent coexistences and sequences in the environment, have any simultaneous and successive changes answering to them in the organism. A plant's vital processes display adjustment solely to the continuous coexistence of certain elements and forces surrounding its roots and leaves; and vary only with the variations produced in these elements and forces by the sun — are unaffected by the countless mechanical and other changes occurring around; save when accidentally arrested by these. The life of a worm is made up of actions referring almost exclusively to the tangible properties of adjacent things. All those visible and audible changes which happen near it, and are connected with other changes that may presently destroy it, pass unrecognized — produce in it no adapted changes: its only adjustment of internal relations to external relations of this order, is seen when it escapes to the surface on feeling the vibrations produced by an approaching mole. Adjusted as are the proceedings of a bird, to a far greater number of coexistences and sequences in the environment, cognizable by sight, hearing, scent, and their combinations; and numerous as are the dangers it shuns and the needs it fulfils, in virtue of this extensive correspondence; it exhibits no such actions as those by which a human being counterbalances variations in temperature and supply of food, consequent on the seasons. And when we see the plant eaten, the worm trodden on, the bird dead from starvation; we see alike that the death is an arrest of such correspondence as existed; that it occurred when there was some change in the environment to which the organism made no answering change; and that thus, both in shortness and simplicity, the life was incomplete in proportion as the correspondence was incomplete. Progress towards more prolonged and higher life, evidently implies an ability to respond to less general coexistences and sequences. Each step upwards must consist in adding to the previously-adjusted relations which the organism exhibits, some further relation parallel to a further relation in the environment. And the greater correspondence thus established, must, other things equal, show itself both in greater complexity of life, and greater length of life — a truth which will be duly realized on remembering that enormous mortality which prevails among lowly- organized creatures, and that gradual increase of longevity and diminution of fertility which we meet with on ascending to creatures of higher and higher development.
It must, however, be remarked, that while length and complexity of life are, to a great extent, associated — while a more extended correspondence in the successive changes, commonly implies increased correspondence in the simultaneous changes; yet it is not uniformly so. Between the two great divisions of life — animal and vegetal — this contrast by no means holds. A tree may live a thousand years, though the simultaneous changes going on in it answer only to the few chemical affinities in the air and the earth, and though its serial changes answer only to those of day and night, of the weather and the seasons. A tortoise, which exhibits in a given time nothing like the number of internal actions adjusted to external ones, that are exhibited by a dog, yet lives far longer. The tree by its massive trunk, and the tortoise by its hard carapace, are saved the necessity of responding to those many surrounding mechanical actions which organisms not thus protected must respond to or die; or rather — the tree and the tortoise display in their structures, certain simple statical relations adapted to meet countless dynamical relations external to them. But notwithstanding the qualifications suggested by such cases, it needs but to compare a microscopic fungus with an oak, an animalcule with a shark, a mouse with a man, to recognize the fact that this increasing correspondence of its changes with those of the environment, which characterizes progressing life, habitually shows itself at the same time in continuity and in complication.
Even were not the connexion between length of life and complexity of life thus conspicuous, it would still be true THE LIFE VARIES AS THE CORRESPONDENCE. 85 that the degree of life varies with the degree of correspondence. For if the lengthened existence of a tree bo looked upon as tantamount to a considerable degree of life; then it must be admitted that its lengthened display of correspondences is tantamount to a considerable degree of correspondence. If otherwise it be held, that notwithstanding its much shorter existence, a dog must rank above a tortoise in degree of life, because of its superior activity; then it is implied that its life is higher, because its simultaneous and successive changes are more complex and more rapid — because the correspondence is greater. And since we regard as the highest life, that which, like our own, shows great complexity in. the correspondences, great rapidity in the succession of them, and great length in the series of them; the equivalence between deo:ree of life and de<2rree of corresoondence, is unquestionable.
§ 33. In further elucidation of this general truth, and especially in explanation of the irregularities just referred to, it requires to be observed, that as the life becomes higher the environment itself becomes more complex. Though, literally, the environment means all surrounding space with the coexistences and sequences contained in it; yet, practically, it often means but a small part of this. The environment of an entozoon, can scarcely be said to extend beyond the body of the animal in which the entozoon lives. That of a fresh- water alga is, virtually, limited to the ditch inhabited by the alga. And understanding the term in this restricted sense, we shall see that the superior organisms inhabit the more complicated environments.
Thus, contrasted with that found on land, the lower life is that found in the sea; and it has the simpler environment. Marine creatures are affected by a smaller number of coexistences and sequences than terrestrial ones. Being very nearly of the same specific gravity as the surrounding medium, they have to contend with less various mechanical actions. The zoophyte rooted to a stone, and the acalephe passively borne along in the current, need to undergo no internal changes such as those by which the caterpillar meets the varying effects of gravitation, while creeping over and under the leaves. Again, the sea is liable to none of those extreme and rapid alterations of temperature which the air suffers. Night and day produce no appreciable modifications in it; and it is comparatively little affected by the seasons. Thus its contained fauna show no marked correspondences similar to those by which air-breathing creatures counterbalance thermal changes. Further, in respect to the supply of nutriment the conditions are more simple. The lower tribes of animals inhabiting the water, like the plants inhabiting the air, have their food brought to them. The same current which brings oxygen to the oyster, also brings it the microscopic organisms on which it lives: the disintegrating matter and the matter to be integrated, coexist under the simplest relation. It is otherwise with land animals. The oxygen is everywhere; but that which is needed to neutralize its action is not everywhere: it has to be sought; and the conditions under which it is to be obtained are more or less complex. So too with that liquid by the agency of which the vital processes are carried on. To marine creatures, water is ever present, and by the lowest is passively absorbed; but to most creatures living on the earth and in the air, it is made available only through those nervous changes constituting perception, and those muscular ones by which drinking is effected. Similarly, the contrast might be continued with respect to the electric and hygrometric variations; and the greater multiplicity of optical and acoustic phenomena with which,terrestrial life is surrounded. And tracing upwards from the amphibia the widening extent and complexity which the environment, as practically considered, assumes — observing further how increasing heterogeneity in the flora and fauna of the globe, itself progressively complicates the environment THE LIFE VAlllES AS THE CORRESrONDENCE. 87 of each species of organism — it miglit finally be shown that the same general truth is displayed in the history of mankind: whose advance in civilization has been simultaneous with their advance from the less varied requirements of the torrid zone to the more varied requirements of the temperate zone; whose chief steps have been made in regions presenting a complicated physical geography; and who, in the course of their progress, have been adding to their physical environment a social environment that has been growing even more involved. Thus, speaking generally, it is clear that those relations in the environment to which relations in the organism must correspond, themselves increase in number and intricacy as the life assumes a higher form.