HISTOPATHOLOGY OF CNS RADIATION 



177 



I'u:. h. Longitudinal section through posterior cohnnns of spinal eord stained with 

 oil red 0, X250, to show the similarity in distribution of droplets stained by this 

 method and vacuoles seen in Gallocyanin-van Gieson (Fig. 5). Same monkey as Fig. 5. 



doses or at the edye of the zone of reaction to find patches of degenerated 

 fibers ( Fis;. 8 ) . 



The distribution, time of demonstration by histologic methods, and the 

 relation to vascular changes all support the vievs- that the effects of gamma 

 and roentgen radiation are direct effects on the parenchyma of the central 

 nervous system and are not mediated through vascular insufficiency. The 

 long latent period before these changes become apparent to the light micro- 

 scopist is a time when the more quickly demonstrable vascular changes 

 dominate the histologic picture. But this does not imply that the vascular 

 lesions are causati\e. It suggests that changes at a submicroscopic, possibly 

 molecular, le\el have been initiated at the time of radiation, changes which 

 are compatible with preservation of morphologic structure for weeks or 

 months. An endpoint must be reached not only before the light microscope 

 can detect the changes, but also before the cellular sequences of repair are 

 initiated. 



