frog may be kept in a state of full bodily vigour for months, or it may be for years; but it will sit unmoved. It sees nothing; it hears nothing. It will starve sooner than feed itself, although food put into its mouth is swallowed. On irritation, it jumps or walks; if thrown into water it swims. If it be put on the hand it sits there, crouched, perfectly quiet, and would sit there for ever. If the hand be inclined very gently and slowly, so that the frog would naturally tend to slip off, the creature's fore paws are shifted on to the edge of the hand, until he can just prevent himself from falling. If the turning of the hand be slowly continued, he mounts up with great care and deliberation, putting first one leg forward and then another, until he balances himself with perfect precision on the edge; and if the turning of the hand is continued, he goes through the needful set of muscular operations, until he comes to be seated in security on the back of the hand. The doing of all this requires a delicacy of co-ordination and a precision of adjustment of the muscular apparatus of the body which are only comparable to those of a rope-dancer."

Now, why have we entered into these details? To reinforce, from a somewhat different point of view, that which has again and again been urged in the preceding sections of this inquiry, that much of animal behaviour is an organic legacy.* A going mechanism of great delicacy, with ready-made coordinations, the products of biological evolution, affords to consciousness a vast body of its primary data. As Dr. Sherrington himself says, "co-ordination is abundantly shown to result from the independent power of the spinal arcs, altogether apart from the influence of the great cranial sense-organs, and of the cerebral arcs superposed upon them. These senses and the brain find the elementary co-ordination of the skeletal musculature an achievement already provided and to hand in the spinal cord. And no doubt the product of the instrument is, with the instrument itself, given over to their use in the reactions they elicit from the spinal musculature." We have seen how instinctive behaviour, in those animals in which it is * Op. cit., pp. 20, 21.

best studied, affords in hereditary biological outline, a sketch which subsequent acquisition, under experience, serves only to elaborate by the filling in of details and of the more delicate shading in behaviour. But in the higher animals, in which a period of youth is a time for the acquisition of experience-for experimentation and practice, it might seem that the inherited biological legacy was of less importance. The "spinal animal,” as Dr. Sherrington calls it, that is, the animal in which the spinal centres are isolated from the cerebral centres—goes far to disprove any such view. In them the cerebral senses and the brain find elementary co-ordination of the bodily movements an achievement already provided and to hand in the spinal cord. But when different animals are compared-frog, bird, rabbit, dog, and monkey-the permanent effects of severance of brain connection, the effects which remain when the temporary period of disturbing "shock" is over, are more marked in the higher than the lower types. And concerning this, Dr. Sherrington says, "The deeper depression of reaction into which the higher animal, as contrasted with the lower, sinks when made spinal, appears to me significant of this, that in the higher types, more than in the lower, the great cerebral senses actuate the motor organs, and impel the motions of the individual."

Whether in the animal in which all direct connection between the anterior and posterior portions of the central nervous system has been severed there is a double consciousness-a cerebral consciousness and a spinal consciousness—we are not in a position accurately to determine. If the generally accepted opinion, that the higher brain-centres constitute the sensorium or seat of consciousness, be correct, we must suppose that a maimed consciousness, with many avenues of experience closed, is retained in the anterior moiety, while the posterior is relegated to a condition of mere sentience at best. In any case all relation between the two is prevented. The two—if two there be-are rendered quite independent through severance of the cord in the region of the neck. But there is a point of view *Op. cit., p. 29.

indicated by Dr. Sherrington which is full of suggestion and interest.

"It is significant in the evolution of animal form," he says, "that the organ that exhibits most uninterrupted and harmonious increase in development, as studied successively in passing from lowest to highest, is the brain. And it is significant that in the nervous system-segmental system as it is— the brain is developed, not in those segments whose sense organs are ordinary cutaneous (tactual, etc.), muscular and visceral, but in the segments connected with the visual, olfactory, and auditory sense-organs; in other words, the brain is developed in the head. The head is, so to say, the individual; it has the mouth, it takes the food, including air and water, and it has the main sense organs providing data for both space and time. To this the body, an elongated motor organ with a share of the viscera and the skin, is appended primarily as a machine for locomotion. This latter must of necessity lie at the behest of the great sense organs of the head."

Now let us try and picture to ourselves a spinal animal, or one which retains only the lowest portion of the brain, the part known as the bulb or medulla oblongata; let us assume that it is conscious and capable of acquiring experience through the association and coalescence of the data afforded by the senses that remain to it; and let us try to imagine the conscious situations which would arise, and their value in the guidance of behaviour. The senses that remain are touch and the temperature sense, the motor sense affording data from the muscles, joints, and tendons, and those which supply certain visceral sensations. There is not one of much, if any, guiding value left. There is not one of what we may term anticipatory use. There is not one which could serve to infuse anything like definite meaning into the situation. For, after all, meaning is expectation. There is an element of anticipation in all those senses which are of any real guiding value in the conscious situation. Sight, hearing, and, especially for some animals, smell, these are the senses which forewarn of *Op. cit., p. 18.

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something which may follow; of other sensations with which in the course of experience they have coalesced. And they are all cut off from the supposed spinal animal. A light touch might in some cases forewarn of the shock or severe pressure, which would perhaps follow. But the shocks would so often come suddenly that it is questionable whether the warning would be of march avail. Still, touch is a warning and cognitive sense, and through it the environment would acquire a limited amount of meaning.

Now, the biological value of coalescent association lies in this very element of warning. The anticipatory senses, sight, hearing, smell, are in their several degrees the "projective' senses, the senses which carry with them the quantity of “outness." And their "projective" character is the necessary psychological expression of their distinctive biological end. They must be projective, must carry with them "outness,” if they are to convey what we, following Dr. Stout, have so often spoken of as meaning. But if the biological value of coalescent association lies in the expectation it renders possible; and if, in the spinal animal, there are no senses left save touch, which could receive from the environment preparatory warning of what is coming; it would seem exceedingly improbable that it should develop quasi-independent conscious situations of its own. In the unmutilated animal, at any rate, tactual experience would most probably coalesce with that derived from the senses which more distinctively take the lead in the acquisition of meaning. And we may therefore, on these grounds, as well as on others, acquiesce in the current view that the quasi-independent functioning of the spinal cord and its constituent segments is, at best, lit up with those flashes of mere sentience of which Sir Michael Foster speaks in the passage we quoted in an earlier section.*

If from the consideration of the isolated spinal animal we turn for a moment to that of the isolated cerebral animal, we find it in a very different position. It is possessed of the warning senses those which from several points of view are * Vide supra, p. 33.

the leading senses-but they are leaders without a following; they have only a very limited company to conduct into action. The company is there, on the further side of the severance, but they have lost touch with it. They know not what it is doing, and have therefore neither the data nor the executive power to guide its manoeuvres in the field of behaviour. They can form maimed coalescent situations, but they are as impotent as a mere theorist devoid of all power of practical application. We need not, however, follow the theme further. We need only add that, could we isolate tracts of nervous tissue in the lower brain-centres of such a cerebral animal, we should find that subsidiary co-ordinations would belong, as a physiological heritage, to these isolated fragments.

The conclusions we may draw, then, with regard to the evolution of behaviour, as viewed in its physiological aspect, are that it is, in its simplest expression and in its most complex, conditioned by sufficient unity of purpose to meet the biological end of survival; that the complex unity of purpose may be analyzed into a multiplicity of subsidiary processes each with its subsidiary unity of purpose; and that the psychological coalescence which gives unity to experience under the guidance of the leading senses, is paralleled in a physiological coalescence within the nexus of the nervous system.

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II. THE BIOLOGICAL ASPECT

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The biological aspect of behaviour-its relation to biological ends has so often come under our consideration in the foregoing chapters that little need be added in this section and that little may be most appropriately devoted, first to the question whether consciousness does influence behaviour; and secondly, this being accepted, to the importance of the rôle that is played by the development of conscious situations in securing, in the higher animals, the biological end of racial preservation.

That this end is secured without the aid of consciousness