HOW WE SEE 



undoubtedly helps to maintain the accuracy of a veiy careful study on this function by 



of detail originating there. Visual acuity Wentworth (96) are shown in Fig. 3. The 



in the periphery of the eye is much less test lights used in the experiment were 



acute than in the fovea due, in part at least, 1° 16' in size, and were isolated from a 



90° 80 



NASAL RETINA 



FOVEA TEMPORAL RETINA 



Fig. 3. The least amount of radiant flux perceptible to the human eye at various retinal locations. 

 The R, B, Y, and G are wavelengths of 672.5, 468, 581.5, and 522 m^, respectively. (Data from Went- 

 worth, 96) 



to the fewer cones and the coarser grouping 

 of them into individual nerve channels. 



Sensitivity of the Retina to Light. As 

 might be anticipated on the basis of the 

 foregoing information, the sensitivity of 

 different parts of the retina to radiant 

 energy also varies considerably. The results 



spectrum at the following wavelengths: red 

 (R) 672.5 mn; yellow (Y) 581.5 m/i; green 

 (G) 522 m/z; and blue (B) 468 m/x. Two 

 obvious conclusions which can be drawn 

 from these data are (1) that the e5^e is most 

 sensitive to radiant energy at some distance 

 from the fovea; and (2) that the eye is not 



