PHYSIOLOGY AND PATHOLOGY. 245
contracting the pupil enables us to see things distinctly even when quite near to us, and this distinctness may be increased by our looking through a hole pierced in a card with a pin; conversely, the pupil is dilated when we look at distant objects. Surely the same movement of the same organ is not likely to proceed alternately from two fundamentally different sources. E. H. Weber 1 relates that he discovered in himself the power of dilating and contracting at will the pupil of one of his eyes, while looking at the same object, so as to make that object appear now distinct, now indistinct, while the other eye remained closed. Johannes Müller 2 also tries to prove that the will acts upon the pupil.
The truth that the innermost mainspring of unconsciously performed vital and vegetative functions is the will, we find moreover confirmed by the consideration, that even the movement of a limb, recognised as voluntary, is only the ultimate result of a multitude of preceding changes which have taken place inside that limb and which no more enter into our consciousness than those organic functions. Yet these changes are evidently that which was first set in motion by the will, the movement of the limb being merely their remote consequence; nevertheless this remains so foreign to our consciousness that physiologists try to reach it by means of such hypotheses as these: that the sinews and muscular fibre are contracted by a change in the cellular tissue wrought by a precipitation of the blood-vapour in that tissue to serum; but that this change is brought about by the nerve's action, and this by the will. Thus, even here, it is not the change which proceeded originally from the will which comes into consciousness, but only its remote result; and even this, properly speaking, only through
1 E. H. Weber, Additamenta ad E. H. Weberi tractatum de motu iridis [Additions to E. H. Weber's treatise on the motion of the iris], Lipsia [Leipzig], 1823.
2 Joh. Müller, Handbuch der Physiologie , p. 764.
