Note 218 — Chapter V · VOLUNTARY AND INVOLUNTARY ACTIONS.

Aubert, Grundrüge der physiol. Optik, 1876, p. 633. “The accommodative movement of the eye is to be considered voluntary. It is true we contract the pupil without being conscious of the contraction of muscular fibres, but this holds good for every voluntary movement. When a person raises the tone of his voice he is not conscious that by muscular contraction he makes his chordæ vocales more tense; he attains his object without being aware of the means by which he does so. The same is applicable to accommodation for near objects and to the contraction of the pupil accompanying it. The fact that this last is only an associated movement does not deprive it of its voluntary character, for there is perhaps no single muscle which can contract entirely by itself.” Donders, On the Anomalies of Accommodation, 1864, p. 574. Professor Beer of Bonn has the rare power of contracting or dilating the pupils of his eye at will; here ideas act as motors. When he thinks of a very dark space the pupil dilates, when of a very bright spot the pupil contracts. (Noble, The Human Mind, 1858, p. 124.) I believe this to be only an exaggerated form of the normal tendency. In all of us the mechanism is so disposed that the feelings of dilatation are associated with feelings (and consequently ideas) of darkness; and by this association a reversal of the process obtains, so that the idea of darkness calls up the feeling it symbolizes.