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H. K. HARTLINE, F. RATLIFF AND W. H. MILLER 



0.5 mm. at the eye 



0,5 ram. at the eye 



Fig. 22. The discharge of impulses from a single receptor unit in response to 

 simple patterns of illumination in various positions on the retinal mosaic. 

 Upper figure: the so-called "Mach pattern" (a simple gradient of intensity). 

 The demagnified image of a photographic plate was projected on the surface of the 

 eye. The insert shows the relative density of the plate along its length as measured, 

 prior to the experiment, by means of a photomultiplier tube in the image plane 

 where the eye was to be placed. The density of the plate was uniform across its 

 entire width at every point. The upper (rectilinear) graph shows the frequency of 

 discharge of the test receptor, when the illumination was occluded from the rest 

 of the eye by a mask with a small aperture, minus the frequency of discharge 

 elicited by a small control spot of light of constant intensity also confined 

 to the facet of the test receptor. Scale of ordinate on the right. The lower 

 (curvilinear) graph is the frequency of discharge from the same test receptor when 

 the mask was removed and the entire pattern of illumination was projected 

 on the eye in various positions, minus the frequency of discharge elicited by a small 

 control spot of constant intensity confined to the facet of the receptor. Scale 

 of ordinate on the left. Lower figure: a simple "step pattern" of illumination. 

 Same procedure as in upper figure. (From Ratliff'and Hartline, 1959). 



