ELEMENTARY EXPERIMENTAL PHYSIOLOGY 25 



(2) Edridge Green's test. Using these cards test your colour 

 visions as directed. 



C. VISION WITH TWO EYES 

 I. What are the Advantages P 



1. Extent of Field of Vision. 



Using the top of the table (p. 22, 5), investigate the field of 

 vision in the horizontal plane first for the right eye, then for the 

 left eye, and then for the two eyes together, taking care not to move 

 the head. Make a diagram of the result, and compare the optical 

 angle in vision with one and with two eyes. 



A 



\LFV 



FIG. 19. To show the Field of Vision for each eye and for the two eyes in 



the horizontal plane. 



A, The point looked at. tf.JF.F.and L.F.V., the right and left field of vision showing the overlap. 

 (From Noel Paton's Essentials.) 



2. Estimation of Contour. 



(a) With the Stereoscope study how the projection of slightly 

 different pictures on the two eyes gives the idea of relief. 



(6) Lay a prism edge on to you on the table, look at it first with 

 one then with two eyes, and consider how the idea of relief is arrived 

 at. 



3. Estimation of Distance. 



Thread an ordinary sewing needle, keeping both eyes open. Now 

 repeat the process with one eye closed. Can it be done with equal 

 readiness ? What conclusion do you draw ? 



Lesson IV. To be provided for each pair of Students. 



1. A blackboard on an easel. 2. Small goniometer made of cardboard. 

 3. Discs of coloured paper, about inch in diameter, true spectral blue, 

 yellow, red, green and white. 



To be provided for Class. 

 1. Perimeter with series of cards. 2. Discs of pure spectral colours 



