2 NEUTRON EFFECTS ON ANIMALS 



For this and other reasons, the report of our work is that of preliminary 

 studies. However, we beheve that it is better to pubhsh what we have 

 done, whether positive or negative, so that others may gain perspective 

 as to the general problem of neutron effects. 



Although radiation is grouped under one term radiations are varied in 

 character; visible light, ultraviolet, X-rays, 7-rays, neutrons, etc., may all 

 be emanations or radiations, but that they have the same mechanism for 

 producing their results is a conclusion so far-fetched and erroneous as to be 

 reached only because of the mystery of the subject. Neutron bombardment 

 and X-radiation may produce somewhat similar results as shown in white 

 blood cell counts and dead cells in pathologic study, but it by no means 

 follows that they achieve these results by a similar mechanism. The cause 

 in both cases may be radiation, and the end results^ — destruction of the 

 cells — may be microscopically similar in the dead tissue, but the inter- 

 mediate mechanism by which these results are attained may be quite 

 different. It may be that neutron and X-ray effects do have a similar 

 mechanism in producing their destructive results, but there is at present 

 no proof that this is so. 



Indeed, we have an example which shows certain lethal radiations have 

 a mechanism which is probably quite different from X-rays. Certain short 

 wave lengths of ultraviolet light are extremely lethal to cells when brought 

 into their proximity and act in an apparently different mechanism from 

 X-rays. 



In 1934, we set up an all-quartz microscope and made a monochromator 

 attachment so that photographs could be taken of the effects of various 

 wave lengths of ultraviolet light measured in Angstrom units. We also 

 made moving pictures of the killing of motile cells such as euglena and para- 

 mecia in order to study the mechanism of their destruction. Cessation 

 of their movement showed that they were killed. 



We found that certain wave lengths of short ultraviolet light were more 

 destructive than others and this because the lethal wave lengths were ab- 

 sorbed by the nucleus of the cell. The absorption of the quanta may be 

 seen by the "blackening" of the nucleus in the pictures of the euglena in 

 Fig. 1 . The three horizontal pictures are different microscopic levels of 

 the same section. It will be seen that, until the neighborhood of wave 



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length 2804 A, there was no absorption of the quanta of ultraviolet light 

 and no killing resulted. When the greatest blackening or absorption of 

 quanta by the nucleus occurred at the line 2536 A, the cells were killed 

 within one or two seconds. Yet the euglena treated by X-rays required 

 20,000 r for 24 hours in order to produce the same lethal results. Lower 



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than 2536 A the absorption was not so great (1). 



