30. These, and analogous facts, have been noted by various experimenters. They are very far from proving what is usually concluded; but they prove the important negative position that the cerebrum is not the centre of innervation for any of the organs on which the observed actions depend. Thus, the cerebrum is not necessary to sight: _ergo_ it does not innervate the eye. It is not necessary to hearing: _ergo_ it does not innervate the ear.[91] It is not necessary to breathing, swallowing, flying, etc.: _ergo_ it does not innervate the organs of these functions.
What then is lost? We have only to remember that the cerebrum is continuous with the thalami and corpora striata, and, through its crura, with the medulla oblongata and medulla spinalis, to foresee that its removal must more or less affect the whole neural axis, and consequently disturb the actions of the whole organism; this disturbance will often have the appearances which would be due to the removal of a central apparatus, so that we shall be apt to attribute the cessation of a function to the loss of its organ, when in fact the cessation is due simply to an arrest of the organ by irritation. Thus the cessation of consciousness, or of any particular movements, when the cerebrum is removed, is no decisive proof that the cerebrum is the organ of consciousness, or of the movement in question. This point will be duly considered hereafter. What we have now to consider is the facts observed after removal of the cerebrum.
First, we observe a loss of that power of combining present states with past states, present feelings with feelings formerly excited in conjunction with them, the power which enables the animal to adjust its actions to certain sensations _now unfelt_ but which _will be_ felt in consequence of the adjustment. Secondly, we observe a loss of Spontaneity: the bird, naturally mobile and alert, now sits moveless for hours in a sort of stupor, occasionally preening its feathers, but rarely quitting its resting-place. All the most conspicuous phenomena which we assign to Intelligence and Will seem absent. The sensations are altered and diminished. Many Instincts have disappeared, but some remain. The sexual feeling is preserved, although the bird has lost all power of directing its actions so as to gratify the desire. But these effects are only observed when the whole of both hemispheres have been removed. If a small portion remain the bird retains most of its faculties, though with less energy. In frogs and fishes there is little discernible effect observed when a large portion of the cerebrum is removed.