586 



RADIATION BIOLOGY 



There is room for some doubt that primary sense cells alone are present 

 in each of the above preparations. Nevertheless, together with work to 

 be described later on single fibers in the optic nerve of Limulus (Hartline 

 and Graham, 1932) and on nerve impulses in Dijtiscus (Bernhard, 1942), 



A 



w 



ppHpMiqpr 



Pi 



■W»H I» (»| i » 



Fig. 13-4. Simultaneous records of action potential and single optic nerve fiber in 

 Limulus. In each record the dashed line at the top marks time in tenths of a second; 

 the short horizontal line shows the duration of the stimulating light; the heavy line 

 shows the action potential recorded by electrodes on the front and back of the eye; 

 and the lighter line shows the responses of a single optic nerve fiber. Records A to 

 D denote responses to stimuli of increasing intensity. Record E shows a calibration 

 consisting of a lOO-yuv square wave. 



these studies strongly support the following conclusions: (1) The action 

 potential is developed by sensory cells, at least in invertebrate eyes. 

 (2) This action potential is generally of the same polarity as the con- 

 stant potential; i.e., the terminal portions of the receptor cells become 

 negative to the basal portions; (3) Some aspect of the action potential 



