250 PSYCHOLOGY. 



of the subdivided angles and lines. Never do we get such 

 strong muscular feelings as when, against the course of na- 

 ture, we oblige our eyes to be still ; but fixing the eyes on 

 one point of the figure, so far from making that part of the 

 latter seem larger, dispels, in most persons, the illusion of 

 these diagrams altogether. 



As for Helmholtz, he invokes, to explain the enlarge- 

 ment of small angles,* what he calls a ' 1<mv of contrast ' 

 between directions and distances of lines, analogous to that 

 between colors and intensities of light. Lines cutting 

 another line make the latter seem more inclined away from 

 them than it really is. Moreover, clearly recognizable mag- 

 nitudes appear greater than equal magnitudes which we 

 but vaguely apprehend. But this is surel}' a sensational- 

 istic law, a native function of our seeing-apparatus. Quite 

 as little as the negative after-image of the revolving spiral 

 could such contrast be deduced from any association of 

 ideas or recall of past objects. The principle of contrast 

 is criticised by Wundt, f who says that by it small spaces 

 ought to appear to us smaller, and not larger, than they 

 really are. Helmholtz might have retorted (had not the 

 retort been as fatal to the uniformity of his own principle 

 as to Wundt's) that if the muscle-explanation were true, it 

 ought not to give rise to just the opposite illusions in the 

 skin. We saw on p. 141 that subdivided spaces appear 

 shorter than empty ones upon the skin. To the instances 

 there given add this : Divide a line on paper into equal 

 halves, puncture the extremities, and make punctures all 

 along one of the halves ; then, with the finger-tip on the 

 opposite side of the paper, follow the line of jDunctures ; 

 the empty half will seem mucli longer than the punctured 

 half. This seems to bring things back to unanalyzable 

 laws, by reason of which our feeling of size is determined 

 differently in the skin and in the retina, even when the 

 objective conditions are the same. Bering's explanation 

 of Zollner's figure is to be found in Hermann's Handb. d. 

 Physiologic, iii. 1. p. 579. Lipps X gives another reason 



* Physiol. Optik, pp. 563-71. 

 t Physiol. Psych., pp. 107-8. 

 i Grundtatsacheii des Seelenlebens, pp. 526-30. 



