HUMAN TOLERANCE TO THERMAL NEUTRONS 



447 



exposed to thermal neutrons, only the tissue comjX)nents were present for 

 interaction. The thermal neutron flux at the skin Icxel was 1.875 X 10'' per 

 square cm per sec. The irradiation time was 502 sec. The reeion of the tumor 

 and the adjacent cortical siuface were exposed to a total of 4.7 X 10" 

 thermal neutrons per scjuare cm. The port was 3.5 in. in diameter. Intrinsic 

 gamma irradiation from the reactor over this period amoimted to 40 r. 

 Death occurred 55 days after irradiation. 



Microscopic examination of the whole brain sections indicated that the 

 residual neoplasm had essentially the same histologic appearance as that 

 noted in the original biopsy. Thus, as far as could be ascertained, the 

 thermal neutrons had no effect on the neoplastic cells. 



The area of the brain adjacent to. and at \arious le\cls distant from, the 

 neoplasm was examined microscopically. In the region at the le\el of the tip 

 of the frontal lobe, a stain for myelin Fig. IBi shows that there is no loss 

 of this material in this region. In contrast, with the same stain (Fig. 2), at 

 the le\el of the genu of the corpus callossum, there is extensive demyeliniza- 

 tion, in all probability due to the presence of the adjacent tumor. In Fis. 3 

 a large mass of neoplasm is shown with partial demyelinization in the ad- 

 jacent area in the right occipital lobe. In contrast, the left occipital lobe 



Fig. IB. Whole brain section of case 8180 r at the le\el of the frontal lobes show- 

 intj a normal mvcHn content and architecture. 



