THE PERCEPTION OF SPACE. 



249 



to both Delboeuf and Wiindt, is owing to the fact that more 

 muscular innervation is needed for the eye to traverse a 

 filled space than an empty one, because the points and lines 



Fig. 6? 



in the filled space inevitably arrest and constrain the eye, 

 and this makes us feel as if it were doing more work, i.e. 

 traversing a longer distance.* When, however, we recol- 



a 



b 



Fig. 



lect that muscular movements are positively proved to have 

 no share in the waterfall and revolving-spiral illusions, and 

 that it is hard to see how Wundt's and Delboeuf 's particular 

 form of muscle-explanation can possibly apply to the com- 

 pass-point illusion considered a moment ago, we must con- 

 clude that these writers have probably exaggerated, to say 

 the least, the reach of their muscle-explanation in the case 



* Bulletins de I'Acad. de Belgique, xxi. 2; Revue Philosophique, vi. 

 pp. 223-5 ; Pbysiologische Psycbologie, 2te Aufl. p. 103. Compare Mlin- 

 sterberg's views, Beitrage, Heft 2, p. 174. 



