406 



INFLUENCE OF EXPOSURE FACTORS 



and not under others. In one study (exposure of about 1 hr) complete 

 additivity was found (72). In another investigation (exposure of 24-48 

 hr) additivity was incomplete (72, 49) (see Table 3). 



The studies comparing x-radiation and neutron exposures on the mi- 

 totic index, the relative numbers and types of chromosomal aberrations, 



TABLE 2 



Comparison of Lethal Effects of X-Rays and Neutrons 



(Single Exposures) 



LD^o LDiiO 



X-Rays, Neutrons, * 



Monkey 



500 



* These are arbitrary units, measured with either a 25-r or 100-r Victoreen chamber. 

 Although these chambers may vary considerably in response to neutron radiation, 

 an approximation of the rep is generally made by multiplying these values of n by 

 2-2.5. 



t Zirkle et al., Comparison of biological action of cyclotron fast neutrons and X-rays. 

 I. Lethal action on mice and rabbits. Con. W-7401-ENG.-37, C.H. 3903, November 

 1950. 



J Report by K. S. Cole et al., Metallurgical Laboratory, University of Chicago, 

 1944. 



§ Rochester Report 5980. 



II Hagen, Jacobson, Murray, and Lear, Metallurgical Laboratory, University of 

 Chicago, 1944. 



