Let us briefly analyze the dog’s condition and actions, reading into them, conjecturally, the accompaniments in consciousness. As he lies on the lawn, he receives a sense-stimulus, auditory or olfactory. It has already acquired meaning, from many a tussle with the butcher’s cur. It has organic effects, and it generates a conscious situation which has acquired complexity through coalescence. As the result of this situation the head is raised, the ears pricked, and so on. The dog is on the alert. His attention is aroused. The muscles of neck, eyes, ears, are brought into play in such a way as to bring the senses to bear on the exciting object. He probably sees the cur through the gap in the hedge. The muscles of the frame are innervated so as to be in a state of preparation to act rapidly and forcibly. At the same time the vaso-motor system is disturbed, the heart-beat is quickened, respiration is altered; there is probably hardly an organ in the body which remains unaffected. Then the dog rushes through the hedge, and stands with bared teeth before his antagonist. A whole set of appropriate muscles are now strongly innervated. There is, perhaps, a double innervation, stimulating to activity and yet restraining from action. He bares his teeth and growls deeply. Attention is so concentrated that he heeds not, perhaps does not hear, his master’s whistle. He is keenly on the alert. The blood-system, respiratory organs, and all his inner machinery are still pulsating with nervous thrills; his back is up. Then he sees his chance, and flies at his opponent. Much that he has learnt in play, and all that he has learnt in earnest, comes to his aid in the short angry scuffle. And what we call his emotion of anger spurs him on to the fight; the cowardly dog in which this is lacking or is replaced by fear is spurred to flight. Each may contribute to self-preservation, but in different ways.
Now, we shall not attempt to determine how the distinctively emotional elements arise. Some think they arise by a sort of irradiating nervous diffusion in the nerve-centres as a direct result of the originating stimulus. Mr. Rutgers Marshall regards them as due to the motor activities in fight or flight; Professor William James contends that they have their source in the visceral affections of heart, lungs, glands, and so forth; Professor Lange attributes them to vaso-motor effects. The problem is a difficult one, and hard to determine by experiment; for we have to deal with a matter of primary genesis, of how they are at the outset introduced into the conscious situation. Experiments on animals which have already gained emotional experience cannot decide the question of genesis. Professor Sherrington, for example, has shown[185] that, after severance of the spinal cord in the lower region of the neck, and of the vagus nerves, by which “a huge field of vascular, visceral, cutaneous, and motor reaction” were “deprived of all connection with the nervous centre necessary to conscious response,” “the emotional states of anger, delight at being caressed, fear and disgust were developed with, as far as could be seen, unlessened strength.” But the avenues of connection were closed _after_ the motor and visceral effects had played their parts in the _genesis_ of the emotion on the hypothesis that the emotion is thus generated. Although new presentative data of this type were thus excluded, their re-presentative after-effects in the situation were not excluded. It is, moreover, an essential part of Professor James’s doctrine, as I provisionally accept it, that the “expression” and the visceral and vascular efforts are independent results of stimulation in certain ways, and that these independent results are conjoined through natural selection. Suppose we sever the connection through which the one takes effect, there is no reason to expect that the manifestation of the other would cease. Professor Sherrington cut off the channels of communication with the visceral and vascular apparatus: if the channels of expression remained open there is no reason why such expression should cease.