Lack of spontaneity, and lack of the power of learning by experience, do not necessarily imply the absence of all consciousness in the widest sense of the word. It would be very rash, therefore, to affirm dogmatically that the frog without its hemispheres is entirely devoid of any kind of feeling. Whether it is so or not is a question which has been much disputed, and we shall not here attempt to decide it. But there is one point which emerges clearly from the experiment: this is that the working of the subcortical mechanism, together with whatever consciousness may accompany it, is capable of taking place separately from, and independently of, processes in the cortex. If this happens when the hemispheres are removed, it may also happen when they are present. In so far as the subcortical centres operate independently of the cortex, any consciousness which may accompany their action will be disconnected from the consciousness which accompanies the action of the cortex. But the consciousness which accompanies intelligent action is associated with cortical process. Now intelligent consciousness, capable of learning by experience, constitutes, in all but the lowest grades of animal life, the main stream of consciousness. Thus, though the independent action of the subcortical centres may not be wholly unconscious, whatever consciousness it involves does not form part of the main current of mental life in man and the higher animals. Only when process in subcortical centres ceases to be separate and independent, and brings into play in a marked manner the action of the cortex, is it accompanied by conscious modifications which form part of the conscious life of the individual as a whole.

This is borne out by human experience. In cases of injury to the spinal cord, the functional connection between lower and higher parts of the cord may be destroyed.

If under these conditions the soles of the patient's feet are tickled, they will be jerked away; but the man himself is in no way aware of what takes place, except as he might be aware of the movement of a foreign body. Quite apart from pathological conditions of this sort, reflex actions are constantly going on, which do not involve in any appreciable way the consciousness of the individual as a whole. The pupil of the eye is constantly contracted and expanded in accordance with varying degrees of illumination. In eating, morsels of food are swallowed by reflex action. We are constantly breathing in the same reflex way. These and similar processes can and do go on while the consciousness of the individual is preoccupied with other matters. On the other hand, there are certain reflex actions, such as sneezing, coughing, and withdrawal of the hand, when suddenly burned or scalded, which usually involve consciousness. A sneeze, for instance, produced by Cayenne pepper, can hardly take place unconsciously. But whenever such actions are unmistakably accompanied by consciousness, it is evident that the stimulus which produces them excites in a conspicuous way the cortex as well as the subcortical centres. Intelligent attention is either brought to bear on the situation, or it is disturbed and deranged by the violence of the shock. When a pin is suddenly plunged into a man's leg, he jumps, by reflex action. But at the same time, there is a marked disturbance of his intelligent consciousness. The train of thought, with which he may have been preoccupied at the moment, is broken off and his whole mental attitude changed. The sensation which introduces a sneeze has not the same violent disturbing effect; but so far as it is conspicuously accompanied by consciousness, it tends to attract attention and to produce intelligent adaptation to circumstances. The man pulls out his handkerchief, or the like. "When the main stream of consciousness is very intently preoccupied, external stimulants which would otherwise excite cortical process, fail to do so and merely produce reflex action of which the individual is unconscious. Thus, when we are much preoccupied with some absorbing object, we may cough or yawn without being aware of it. From the facts we have stated, we may conclude that the cortex is preeminently, if not exclusively, the seat of those processes which are immediately correlated with individual consciousness.

Besides being a mechanism of reflex action, the subcortical centres constitute an apparatus by means of which the cortex produces movements of the organism. The mechanism for the relatively simple constituents of complex activities is contained in the subcortical centres. The complex activities are produced by the cortex playing upon the lower centres, so as to evoke the simple constituent movements in a certain order, simultaneous and successive. It is, above all, the successive coordination of movements which is due to the cortex. Simultaneous coordination of a complex kind is involved in many purely reflex actions.

From a biological point of view, the function of the cortex is adaptation to irregularly varying conditions. Keflex action will suffice to maintain the life of an animal which has merely to perform simple actions in a uniform way on the recurrence of uniform external conditions. But where fluctuating adaptation to fluctuating conditions is required, reflex action becomes inadequate, and often actually harmful. Action must be varied in correspondence with the results of previous action, so that it may not be repeated in circumstances under which it has proved injurious. For this, intelligence, and the nervous organization correlated with intelligence are required. The burnt child shuns the fire, and so saves itself from future burns; but the moth will dash again and again into the candleflame, though it is singed every time. The moth's action is reflex, that of the child is intelligent.