Photoreception 



421 



by illumination, called the retinal action potential, is such as to cause an in 

 crease in the electrical negativity of the apical ends of the photosensitive ele- 

 ments (Fig. 15, B, right). The magnitude of the retinal action potential is 



OffOANISM RECOR. CIRCUIT 



INTENSITY 



CEPHALOPOD 



/fOSCHAT/^ 

 PIPER-I9I( 



STRING 

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Electrical response. 



0.5 SECOND 



HORSESHOE CRAB 



MATTHEWS 



PoiY/Vf£Af^3 Oscillograph 



eRAHAn-l93Z ^^ AMPLIFIER 



HARTLINE & GRAHAM 



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GRASSHOPPER 



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SSCILLX3GRAPH 



FROG 



PIPER -191 1 

 AND 



NIKIFOROWSKI 



STRING 

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CITED BY KOHLRAU5CM 

 1931 



MAN&Vt^lTERAT INK OSCILLOGRAPH 



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 ADRIAN-1945 A-C AMPLIFIER 



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Fig. 127. Retinal action potentials of different animals obtained under somewhat 

 different conditions. Upward deflection in all cases indicates negativity of the electrical 

 lead near the free end of the retinal cells. The magnitude of the responses is not com- 

 parable because of differences of amplification. 



greatest shortly after the onset of illumination (the b-wave). As illumination 

 continues, the electrical response may decline rapidlv to a minimum which 

 is maintained (Fig. 127, Limidiis eye), or the electrical response may in- 

 crease in magnitude again (the c-wave) after a slight decrease (Fig. 127, 



