500 PAUL S. HENSHAW 



taking into account the precise nature and relative influence of each, a 

 ground work is laid for systematic assessment of residual capabilities in eco- 

 entities of any level of organization, with or without irradiation. 



Analysis of the effects of low level environmental radiation on the nervous 

 system yields a double return; in addition to contributing to an understand- 

 ing of the practical problem of irradiation hazards to individuals and popula- 

 tion groups, it provides fundamental information about the operational 

 character of the nervous system. 



Preliminary findings that appear to have meaning are: (a) the older the 

 fetus, the greater the dose required to produce decrements in learning, sug- 

 gesting that since cerebral cellularity appears to vary correspondingly, learn- 

 ing must somehow be associated with the number of cells in the adult brain; 

 (b) improvements in certain performance capabilities following irradiation, 

 upon careful analysis may be found to stem from reduced distractability, a 

 deleterious rather than a beneficial efTect; (c) the more refined the tech- 

 niques used and the more complex the nervous system studied, the easier it 

 is to demonstrate a radiation-induced modification, suggesting that the 

 advanced human nervous system may be more easily afTected by radiation 

 than the nervous systems of other species; and (d) late effects, consisting 

 mainly of altered rates of degenerative changes, are difficult to demonstrate, 

 requiring time-consuming and costly techniques. 



References 



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Bachofer, C. S. 1957. Enhancement of activity of nerves by x-rays. Science 125, 1140- 

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Brown, W. L., Carr, R. M., and Overall, J. E. 1959. The effect of whole body irradia- 

 tion upon association of peripheral cues. Gen. Psychol. 61, 113-119. 



Brown, W. L., Overall, E., Logie, L. C, and Wicker, J. E. 1960. Lever-pressing be- 

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Furchtgott, E., and Echols, M. 1958a. Locomotor coordination following pre- and 

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