ences with Medicine1 (1881)—and indicates certain modifications of Descartes's views which more recent biological conceptions had seemingly rendered necessary. He says: 2

"But though, as I think, there is no doubt that Descartes was the first to propound the fundamental conception of the living body as a physical mechanism, which is the distinctive feature of modern, as contrasted with ancient physiology, he was misled by the natural temptation to carry out, in all its details, a parallel between the machines with which he was familiar, such as clocks and pieces of hydraulic apparatus, and the living machine. In all such machines there is a central source of power, and the parts of the machine are merely passive distributors of that power. The Cartesian school conceived of the living body as a machine of that kind."

Professor Huxley then leads up to the modern conception of the animal body as constituted by a multitude of cell-units, together with certain of their products; and quotes from Bichat the following intermediate conception:

"All animals," says Bichat, "are assemblages of different organs, each of which performs its function and concurs, after its fashion, in the preservation of the whole. They are so many special machines in the general machine which constitutes the individual. But each of these special machines is itself compounded of many tissues of very different natures, which in truth constitute the elements of these organs."3

In view of this conception of the body as a complex structure composed of special organs and tissues, supplemented by the more recent conception of the tissues themselves as constituted of cellular units, Descartes's views stand in need of restatement, and Huxley thus indicates the nature of the modification required:

"The proposition of Descartes that the body of a living man is a machine, the actions of which are explicable by the known laws of matter and motion, is," he says, "unquestionably largely true. But it is also true, that the living body is a synthesis of innumerable physiological elements [the cell-units], each of which [is] susceptible of structural metamorphosis and functional metabolism: and that the only machinery, in the precise sense in which the Cartesian school understood mechanism, is that which co-ordinates and regulates these physiological units into an organic whole."4

1Collected Essays, Vol. III., pp. 350 et. seq. Loc. cit., pp. 368-369.

Loc. cit., p. 367.

2Loc. cit., pp. 362–363.

Huxley then proceeds to show that, with regard to the action of the living protoplasm of the cell unit, physiologists fall into two schools. First, those "who look with as little favor as Bichat did upon any attempt to apply the principles and the methods of physics and chemistry to the investigation of the vital processes of growth, metabolism, and contractility;" and secondly, those who "look to molecular physics to achieve the analysis of living protoplasm itself into a molecular mechanism." And he himself accepts the latter alternative. "Living matter," he says, "differs from other matter in degree and not in kind; the microcosm repeats the macrocosm; and one chain of causation connects the nebulous original of suns and planetary systems with the protoplasmic foundation of life and organisation."1

So far good. Professor Huxley, however, does not proceed, with his accustomed thoroughness, to exhibit the connexion of this conception of cellular automatism with the modified Cartesian view, according to which, he says, the only machinery is that which coordinates and regulates these physiological units into an organic whole. I may perhaps be permitted to do so in terms of that restricted automatism which I am here advocating.

Every cell may be regarded as a minute machine specially fitted to produce certain chemical products or to undergo certain physical changes under the conditions which obtain in the living body. Groups of these minute cellular machines constitute tissues and organs in which their joint and related activities are effectively combined. The organ thus forms a composite machine; and its products or its physical changes are the net result of the mechanical transactions in the cell units of which it is constituted. And the machine is an automatic one in the sense that every physical change which occurs therein has physical antecedents or causes. But it also presents this peculiarity; that the structure of the machine is modified by its functional activity; that it is to some extent a plastic machine which is moulded to its work by the performance of that work. So that if we speak of it as a piece of automatic mechanism

1Loc. cit., pp. 370–371.

we must remember that its automatism is, within certain limits, capable of adaptive modification; that there is in addition to automatic performance and automatic adjustment something more, namely adaptation to new conditions. Whether it is well to apply the term "automatic" to such adaptation is a matter that is open to discussion. The conception of automatism carries with it, for me, an idea of relative fixity and invariability with which the idea of plasticity and adaptation is incongruous; and I should myself prefer to say that organic adaptation to environing conditions is something beyond and superadded to automatism.

We must in any case distinguish between the multifarious molecular processes which occur in muscular and glandular tissues and the co-ordinating processes which occur in nervous centres, and which serve to give unity to the working of the compound mechanism of the body at large. It is here that we find that machinery, "in the precise sense in which the Cartesian school understood mechanism," which regulates the activities of the physiological units and co-ordinates them into an organic whole. But there are two distinct types of the regulative process involved in this coordination; the one characterised by relative fixity and invariability; the other characterised by relative plasticity and adaptation. It is to the former that the term animal automatism is, I conceive, properly applicable. It comprises that co-ordination which is seen in reflex action and in instinctive response. It involves no intervention of conscious guidance and control. In so far as it is subject to modification it ceases to be automatic in character. Strongly contrasted with this type of regulative co-ordination is that which gives plasticity to the organism as a whole. It comprises that coordination which is seen in voluntary action and renders acquisition possible. It exercises a more or less modifying influence on instinctive responses and thus lifts them above the level of automatism. It involves the direct intervention of those molecular cortical processes which have for their conscious concomitants what we term choice, based on previous individual experience and dependent upon the association of impressions and ideas.

On this view an intelligent (and still more a rational) automa

ton is a contradiction in terms. Intelligence takes in hand the automatism presented through heredity, modifies it, and, in the early days of life drills the activities and reorganises them into habits.

When a drill sergeant takes in hand a number of raw recruits he has to keep a vigilant eye on all their actions, checking useless, misguided, or mistaken activity in this direction, eliciting more prompt and more vigorous response to his commands in that direction; making his men act not as isolated units but as constituent members of a corporate body, and aiming throughout at that coordinated action on which their future efficiency will depend; so that, when they take their places in the ranks, each may be ready to perform his own part, in due subordination to the combined action of the whole, without faltering and without hesitation. The men are duly organised into squads, companies, battalions, and so on; and thus we have a disciplined army with its brigades, divisions, and army corps; with its artillery, engineers, cavalry, and infantry; with its staff divided into intelligence, commissariat, and medical departments, each with distinctive responsibilities and under its own especial commanding officers; the whole capable of the most varied and yet most orderly evolutions at the will of the commander-in-chief.

It is the function of consciousness, represented in the flesh by the cerebral cortex, to drill and organise the active forces of the animal body in a somewhat analogous manner. But when it enters upon its duties consciousness finds that a considerable amount of the drilling has already been done for it. There is no need to teach the organic mechanism how certain activities are to be performed. They are already carried out automatically. The intelligence department, with its special senses and so forth, is already organised so far as the supply of information is concerned. The commissariat department, digestive organs, heart, lungs, and the rest, is in pretty good working order and eagerly on the look-out for supplies. Many complex activities, adaptive actions of the reflex kind and of the type termed instinctive, are at once performed without the guidance of consciousness under appropriate conditions. Consciousness merely looks on and makes a memorandum of what is going for

ward.

The number and the complexity of those instinctive activities that consciousness thus finds ready to its hand varies in the different grades of animal life; being at a maximum in such forms as insects and spiders; being more marked in birds than in mammals; and being inconspicuous or difficult to trace in man. There are, however, also many more or less isolated activities, with very little initial adaptive value, which resemble raw recruits. Such are the comparatively aimless and random limb-movements of the human infant, as he lies helpless on his mother's lap. Consciousness has to lick these into shape; to combine and organise their vague efforts in directions that are useful for the purposes of animal life, and adapted to the conditions under which the forces of that life are employed; gradually to bring the effective work done by the several companies, represented by groups of muscles, into due relation to each other; and to assume the supreme command of all the forces and thus to carry on the battle of life at the best advantage.

Such an analogy as this must not be pressed too far. It is adduced merely for the purposes of illustration. The drill-sergeant, for example, is dealing with intelligent beings themselves capable of directing and controlling their own actions. But consciousness as a drill-sergeant is dealing with automatic movements or activities, instinctive or random as the case may be, themselves incapable of self-guidance. What the analogy here serves to illustrate is this, that neither the drill-sergeant, on the one hand, nor consciousness, on the other hand, can directly produce the activities which are dealt with. The activities must be given. The utmost that can be done is to stimulate some to increased energy of action and to check or repress others. The activities cannot be created or produced: they can only be educed or reduced. Secondly, just as the drill-sergeant must vigilantly watch his men, since he is dependent on such observation for information as to the correct performance of their actions; so, too, is consciousness entirely dependent on the information received through the incoming channels or afferent nerves for the data upon which its guidance, through the exercise of its power of augmentation, and inhibition, is based. Thirdly,