untary acts there is no line to be drawn. In deliberative acts the sense of effort is associated with the conflict of ideas and motives, and belongs to the sensor centres. The act of willing consists essentially in a consent to the occurrence of a movement, the movement itself being prefigured by certain revived impressions, visual, or auditory, or kinesthetic. The activity of these sensor centres awakes a corresponding activity in the motor centres of the bulb or spinal cord. There is no reason for postulating motor centres in the cortex; the so-called motor centres of the Rolandic tract are of the kinesthetic type and intimately connected with visual, auditory, and other sensor centres. The process of attention is accordingly essentially sensory, and volition, representing certain phases in the association of ideas, is likewise sensory. The motor processes taking place in the bulb and spinal cord are, however, outside of consciousness.
Wundt explains the overestimation of certain forms of linear and angular magnitude by reference to feelings of relative exertion in the motions of the eye. Besides failing to show how we get ideas of distance out of feelings of exertion, the theory rests on the unproved assumption that in measuring form and size the eye fixes in rapid succession a series of points. Given the consciousness of space, feelings of exertion might serve as signs for spatial determinations. It is doubtless true that we measure off space with the muscles of the eye, as with other muscles, especially of the neck; but this is only the determination of the position of a certain visual field in the series of possible fields, and has nothing to do with measurements within a given field. Phenomena of displacement of the visual field arising from paralysis of the eye muscles do not concern measurements within the field. James says we see depth directly, but as a matter of fact the visual field has neither depth nor form except what we ascribe to it by way of inference. On the basis of experience, the sensations arising from convergence of the eyes become signs of depth. Wundt holds that the original form of the monocular visual field is spherical, but there is no proof the monocular field was ever spherical; we formed the binocular field of vision first, and the monocular field may be only a reproduction of the binocular. Moreover, why not take the plane surface of the earth up to the horizon line as the original field, instead of the curved form of the sky? The oblique position of vertical lines seen in indirect fixed vision Wundt regards as a direct proof of his theory of motions of the eye. Wherein it is a proof is not easy to see. The
