NEUTRON EFFECTS ON ANIMALS 6 



O 



The line 2536 A of ultraviolet light is the most lethal wave length yet dis- 

 covered. It is hundreds of times more lethal to cells than high voltage 

 X-rays. Its disadvantage is the lack of penetration through tissues. 



The partial mechanism of this wave length is the absorption of the quanta 

 by the nucleic acid of the nucleus of the cell since nucleic acid has an ultra- 

 violet spectrographic peak, an extinction coefficient, in the neighborhood of 



Z804 f( 





3B54 tf 



4D47A*' 



M\ 



i.;/^^-Vv~ 



'^%'Z 



->V,\ 



Fig. 1. Euglena killed h\ ultraviolet light— 2535 A 



2536 A: it is a resonance effect and a similarity of absorption coefficient. 

 These shorter ultraviolet wave lengths apparently break down certain of 

 the molecular bonds, particularly the polypeptide linkages which are so 

 frequent in the amino acids. 



That the same course is followed in X-ray effects seems ^•ery doubtful 

 for there is little or no "blackening" of the cell nucleus by X-rays. It may 

 be possible that the killing effect of X-rays is due to secondary radiation 

 with production of wave lengths at a lower wave length, a Compton-Ein- 

 stem effect, in the neighborhood of 2536 A, but there is little or no evidence 

 as to this. When the enormously greater energy delivered by X-rays is 



