278 



C. T. GAFFEY 



nerve of each pair was irradiated, while its companion functioned as a 

 control. 



To determine neural activity, a nerve was placed on Ag-AgCl electrodes 

 in a moist chamber (Fig. 1) through which circulated a mixture of 95% 

 oxygen and 5% carbon dioxide saturated with water vapor after passage 

 through 3 gas-washing cylinders. Monophasic, rectangular stimuli 0.1 milli- 

 sec in duration were delivered from a Grass stimulator (Model S-5) through 

 an isolation unit to the nerve at 60 pulses per second. Recording electrodes 

 detecting the propagated neural impulse ran to a push-pull, A. C. pre- 

 amplifier (Grass Model P-5), which then fed the signal into a Textronic 

 oscilloscope (Model 532) with a high-gain, differential input amplifier (Tex- 

 tronic type 53/54 D). In conduction velocity studies a fast rise, dual-trace 

 input stage amplifier (Textronic type 53/54 C) was employed. The dis- 

 played action potentials were photographed by a Fairchild polaroid oscillo- 

 scope camera (Model F-286"). 



The Lawrence Radiation Laboratory's 184-in. frequency modulated cyclo- 

 tron was available as a source of 910 Mev alpha particles and 455 Mev deu- 

 terons (Tobias et al, 1952, 1958). By appropriate magnetic focusing tech- 

 niques, these high energy nuclei were made to travel in parallel, approxi- 

 mately monoenergetic beams. An ionizing chamber placed in front of the 

 bombarded nerve was used to monitor the delixered dose (Birge et al., 

 1956). A summary of the specifications of the 184-in. synchrocyclotron is 

 presented in Table L 



\ Outflow 



Electrodes 



Inflow of water saturated 

 95% Og + 5% COg 



Fig. 1. Lucite chamber for keeping a nerve moist during the study of propagated 

 potentials. Electrodes (1) and (2) are stimulating electrodes, while recordings can 

 be made from electrodes (3) and (5) or (4) and (5). The distances from the first 

 electrode are: 3 mm, 15 mm, 30 mm, and 40 mm. 



