134 Applied Biophysics 



tion, was thereby diminished compared with a very short ex- 

 posure. 



Mouse tumor tissue has also been irradiated by the very 

 densely ionizing particles resulting from the disintegration of 

 boron or lithium by slow neutrons. Very great technical diffi- 

 culties were encountered in obtaining quantitative results in the 

 in vivo experiments. An effect of the disintegration particles 

 was clearly demonstrated in the /';/ vitro experiments/^ though 

 it was not possible to estimate their efficiency relative to other 

 ionizing radiations. 



Neutron Therapy 



In 1942, Stone and Larkin -^^ reported upon 92 patients suffer- 

 ing from malignant disease who had been treated by neutrons. 

 With regard to the clinical results, it is best to quote Stone's ^^ 

 views : 



"It is difficult, in discussion of effects of a method of treatment 

 tried almost entirely on patients with far advanced cancer, to 

 convey any adequate idea of what actually takes place during 

 the course of treatment. While the ' survival statistics presented 

 and the autopsy findings reported appear discouraging, the .general 

 impression of one watching the patients being treated is that 

 marked tumor regressions are being produced even when they 

 were not expected. In many instances, large metastatic nodal in- 

 volvements disappeared, showing a remarkable effect of the 

 neutron rays on the tumors. The patients as a whole did not react 

 so well, either because the tumor had spread beyond the treated 

 regions and was not controllable for that reason, or because a 

 debilitating ulcer remained at the site of the primary node. In 

 many instances, biopsies from the edges of persisting ulcers did 

 not show evidence of cancer, but because of either the extensive 

 destruction caused by the cancer or the irreparable damage caused 

 by the neutron rays, normal tissues would not react in such a 

 way as to bring about the healing of the ulcer." 



Skin reactions to neutron radiation followed the same general 

 course as after X-radiation. Considerablv smaller doses of 



