486 W. MCDOUGALL but chiefly those of the sense organ whose excitement has initiated these motor effects, for, as we have seen above in the case of the two eyes, the afferent influx from the intrinsic muscles of one eye re-enforces the sensations of that eye much more strongly than those of the other eye. We must assume then that the afferent tract from the intrinsic muscles of FIG. 9. either eye is specially connected with the tract leading from the retina of that eye, so that the excitation process initiated in it by contraction of the muscles discharges not only through the motor-circle but in part through the retino- cerebral tract, augmenting in the latter the excitement which is directly due to the visual stimulus. How exactly the two
