But these matters are of little moment to anyone but the Reviewer and those persons who may incautiously take their physiology, or psychology, from him.  The really interesting point is this, that when he fully admits that animals “may possess all the first four groups of actions,” he grants all that is necessary for the purposes of the evolutionist.  For he hereby admits that in animals “impressions received result in sensations which give rise to the observation of sensible objects,” and that they have what he calls “sensible perception.”  Nor was it possible to help the admission; for we have as much reason to ascribe to animals, as we have to attribute to our fellow-men, the power, not only of perceiving external objects as external, and thus practically recognizing the difference between the self and the not-self; but that of distinguishing between like and unlike, and between simultaneous and successive things.  When a gamekeeper goes out coursing with a greyhound in leash, and a hare crosses the field of vision, he becomes the subject of those states of consciousness we call visual sensation, and that is all he receives from without.  Sensation, as such, tells him nothing whatever about the cause of these states of consciousness; but the thinking faculty instantly goes to work upon the raw material of sensation furnished to it through the eye, and gives rise to a train of thoughts.  First comes the thought that there is an object at a certain distance; then arises another thought—­the perception of the likeness between the states of consciousness awakened by this object to those presented by memory, as, on some former occasion, called up by a hare; this is succeeded by another thought of the nature of an emotion—­namely, the desire to possess the hare; then follows a longer or shorter train of other thoughts, which end in a volition and an act—­the loosing of the greyhound from the leash.  These several thoughts are the concomitants of a process which goes on in the nervous system of the man.  Unless the nerve-elements of the retina, of the optic nerve, of the brain, of the spinal chord, and of the nerves of the arms went through certain physical changes in due order and correlation, the various states of consciousness which have been enumerated would not make their appearance.  So that in this, as in all other intellectual operations, we have to distinguish two sets of successive changes—­one in the physical basis of consciousness, and the other in consciousness itself; one set which may, and doubtless will, in course of time, be followed through all their complexities by the anatomist and the physicist, and one of which only the man himself can have immediate knowledge.