human
In the substances of which organisms are composed, the conditions necessary to that redistribution of Matter and Motion which constitutes Evolution, are fulfilled in a far higher degree than at first appears. Thus the most complex compounds into which Carbon, Hydrogen, Oxygen, and Nitrogen enter, together with small proportions of two other elements (Sulphur and Phosphorus) which very readily oxidise,
gpt
; the component elements have an unusual tendency to unite in different modes of aggregation though in the same proportions, thus forming analogous substances with different properties; the colloid character of the most complex compounds that are instrumental to vital actions gives them great molecular mobility--a plastic quality fitting them for organisation;
human
;
gpt
It follows from the law of the Conservation of Energy that
human
The materials forming the tissues of plants as well as the materials contained in them, are progressively elaborated from the inorganic substances; and the resulting compounds, eaten, and some of them assimilated by animals, pass through successive changes which are, on the average, of an opposite character: the two sets being constructive and destructive. To express changes of both these natures the term 'metabolism' is used; and such of the metabolic changes as result in building up from simple to compound are distinguished as 'anabolic,' while those which result in the falling down from compound to simple are distinguished as 'katabolic.'
gpt
Regarded as a whole, metabolism includes, in the first place, those anabolic or building-up processes specially characterising plants, during which the impacts of ethereal undulations are stored up in compound molecules of unstable kinds; and it includes, in the second place, those katabolic or tumbling-down changes specially characterising animals, during which this accumulated molecular motion (contained in the food directly or indirectly supplied by plants) is in large measure changed into those molar motions constituting animal activities. There are multitudinous metabolic changes of minor kinds which are ancillary to these--many katabolic changes in plants and many anabolic changes in animals--but these are the essential ones.
human
But he soon saw that this was too wide.
gpt
It may be said of the Solar System, with its regularly-recurring movements and its self-balancing perturbations, that it, also, exhibits co-ordination of actions.
human
A true idea of Life must be an idea of some kind of change or changes. Therefore he carefully considered assimilation on the one hand, as an example of bodily life, and reasoning on the other hand, as an example of that life known as intelligence, and inquired into the common features of these two processes of change. Thus there emerged the formula that life is _the definite combination of heterogeneous changes, both simultaneous and successive_. But this formula also fails, as he said, by omitting the most distinctive peculiarity. It is universally recognised that living creatures continually exhibit _effective_ response to external stimuli. To be able to do this is the very essence of life, distinguishing its responses from non-vital responses. Thus a clause must be added to the proximate conception, and the formula reads:
gpt
Life is the definite combination of heterogeneous changes, both simultaneous and successive, _in correspondence with external co-existences and sequences_. There are internal relations, namely,
human
and there are external relations,
gpt
and life is the connexion of correspondence between them. Thus under its most abstract form, Spencer's conception of Life is:--
human
The idea of co-ordination is so cardinal a one that it should be expressed not by implication but overtly. The formula defining the phenomenon of life thus reads:
gpt
It may be needful to remark that this was not intended to define Life in its essence, but Life as manifested to us.
human
The ultimate mystery is as great as ever: seeing that there remains unsolved the question: What _determines_ the co-ordination of actions?
gpt
As organisms become more differentiated they enter into more complex relations with their environment, and as the environment becomes more complex organisms become more differentiated. The internal and external relations increase in number and intricacy _pari passu_, and the correspondences between them become more complex, numerous, and persistent.
human
The highest life is 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.
gpt
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.
human
This continuous correspondence between inner and outer relations which constitutes Life, and the perfection of which is the perfection of Life, answers completely to that state of organic moving equilibrium which arises in the course of Evolution and tends ever to become more complete.
gpt
When it is said that Life is the definite combination of heterogeneous changes, both simultaneous and successive, in correspondence with external co-existences and sequences, there arises the question--Changes of what?... Still more clearly do we see this insufficiency when we take the more abstract definition-- the continuous adjustment of internal relations to external relations.
human
Is this principle of activity inherent in organic matter, or is it something superadded?