VISION 



195 



(1) Examine the upper median quadrant by sweeping a white test 

 object around arc 60 degrees, keeping the test object as near the 

 surface of the chart as possible. If the subject does not see it at 

 all, try latitude 50 degrees. Having located the circle which seems 

 to be near the boundary, locate upon each meridian a point which 

 indicates the limit of indirect vision in that direction. Join with a 

 continuous line the points located, thus enclosing an area of indirect 

 vision. 



(2) Test the lower median quadrant in the same way. Is the total 

 area covered by indirect vision in this quadrant greater or less in 

 extent than that in the upper quadrant? 



370 



Perimeter chart, upon which the blackboard perimeters are to be transcribed for permanent 



record. 



(3) Test the upper lateral quadrant and then the lower lateral 

 quadrant. Are these two quadrants practically equal? Is there any 

 ready explanation why the outer two quadrants should contain such 

 an excess of area over the inner two quadrants? 



(4) To Record the Perimeter Outline. For this purpose one 

 should have printed charts like the one given in Fig. 82. Note that 

 here the circles are equidistant. They represent concentric arcs of a 

 quadrant with 10 degrees of the circle between each two, while the 

 circle upon the blackboard chart represents a radial projection of these 

 arcs upon a plane tangent to the sphere at the point of fixation. 



In transcribing the perimeter upon the record chart one has only 



