INHIBITORY INTERACTION IN THE RETINA 



249 



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TIME - SECONDS 



Fig. 7. Inhibition of the discharge of impulses from an ommatidium produced 

 by illumination of a nearby retinal region for a period of 3 sec at a high intensity 

 (top graph, log / inhib = 0), and at a low intensity (middle graph, log / 

 inhib = 1-5), with a control for comparison (bottom graph). Frequency of 

 discharge (reciprocal of interval between successive impulses) is plotted as 

 ordinate vs. time (sec) as abscissa. From oscillograms similar to that of Fig. 6. 

 Throughout this paper the "magnitude of inhibition" is measured by the differ- 

 ence, over corresponding periods of time, between the frequency in the control 

 and the frequency during the inhibiting illumination. (From Hartline et al., 1956). 



an appreciable delay in the onset of inhibitory effect. Also, a recognizable dip 

 in frequency appears at the beginning of the period of antidromic stimulation, 

 even though the antidromic impulses were uniformly spaced. Inhibition in 

 the eye of Limulus has an appreciable lag, and shows something akin to 

 adaptation. 



