THE SENSE ORGANS 



one another. Between A and B make several dots of equal size. A 

 and B will then appear farther apart than B and C (Fig. 117). 



(c) Draw two horizontal lines of equal length and parallel to one 

 another. Upon the ends of one draw oblique lines outward and upon 



FlG. 118. MULLER-LYER FIGURES TO SHOW ILLUSION IN SPACE PERCEPTION. THE LlNES 



A AND B ARE OF THE SAME LENGTH. 



the ends of the other similar lines turned inward. The latter will then 

 appear to be shorter than the former. 



(d) Draw two lines of equal length parallel to one another. Next 

 to this figure draw another of the same dimensions with several inter- 



FIG. 119. To ILLUSTRATE THE OVERESTIMATION OF VERTICAL LINES. 



coursing lines. Note that the second figure appears to be larger than 

 the first (Fig. 117). 



(e) Place a vertical line beside a horizontal line of the same length. 

 The former appears to be the longer (Fig. 119). 



