180 ORVILLE T. BAILEY 



-Campbell and Novick (1949) have found that astrocytes are most suscep- 

 tible to beta radiation, oligodendroglia and microglia being highly resistant. 

 Haymaker et al. (1958), using barium^'*"-lanthanum^^'^' as the source of 

 gamma radiation obtained results which diflfered from those of Arnold and 

 P. Baifey ( 1954) with roentgen radiation. They conclude that alterations in 

 glial cells are relatively inconspicuous. It is difficult to reconcile these two 

 observations. 



Personal studies of material using Ta^*"- as a source of gamma radiation 

 give results entirely in agreement with those obtained by Arnold and P. 

 Bailey (1954). While the experimental procedure was not suitable for the 

 study of early changes, the specimens studied at relatively short intervals 

 after radiation showed disintegration of oligodendroglia coextensive with 

 myelin loss and almost complete, if not total, inhibition of compound gran- 

 ular corpuscle formation. The disintegration of astrocytes extended through- 

 out the area of maximum radiation effect and for a short distance beyond 

 where neurons were demonstrably afTected. In later stages, the inhibition of 

 the expected astrocytic proliferation was a striking feature of the radiation 

 response, but at the longest internals (up to 3 years) after radiation, brisk 

 astrocytosis was again resumed. It is difficult to be precise in regard to the 

 time when astrocytes begin to respond in the expected way as a part of the 

 sequences of repair. Arnold and P. Bailey (1954) placed it at "many 

 months." Our material can make this interval no more exact. 



Behavior of Collagen in Radiated Areas and its Significance in 

 Reparative Sequences 



Little attention has been paid to the effects of ionizing radiation on the 

 collagen of the central nervous system parenchyma. Confined as it is under 

 normal conditions to the region of blood vessels, it is relatively inconspicuous. 

 However, it is important in the normal nei'vous system and participates in 

 reparative sequences. 



In personal material, the growth of collagen is the dominant feature of 

 the initial tissue response in brain and spinal cord areas where radiation has 

 produced total necrosis. This type of lesion has been studied to best advan- 

 tage in the spinal cord where no operative procedure had been carried out 

 within the parenchyma. Necroses studied a few weeks or months after radia- 

 tion fail to show any evidence of cellular repair (Fig. 9), a finding in agree- 

 ment with Arnold and P. Bailey (1954). Some of these necroses extend 

 completely across the spinal cord (Fig. 9) and occasionally a part of the 

 necrotic material protrudes as small elevations into the subarachnoid space 

 in small zones of partial destruction of the pia (Fig. 10). No instances of 

 complete necrosis of the pia or escape of necrotic material into the subarach- 



