LAMINAR LESIONS IN CEREBRAL CORTEX 



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the lesion may be as narrow as 60 a*: with higher doses which produce 

 typical laminar destructions this width is close to 180 m; still higher doses 

 may produce lesions over 200 M wide. (All the figures refer to stained 

 preparations. ) 



One striking observation in regard to the laminar lesions is that their 

 glial content is moderate in animals sur\iving 6 weeks or longer. In Fig. 1 

 the glial content of the laminar lesions appears approximately the same as 

 that of the zonal lamina. This is typical, even though a laminar lesion in 

 early stages displays a vascular and glial reaction, which may be intense 

 if the radiation dose is nearly maximal for laminar destruction. 



We have conclusive evidence that older laminar lesions regularly display 

 dendritic processes and a wealth of axons which form irregular and often 

 denser patterns than do normal cortical sectors (Figs. 2-4). In Figs. 2-4, 

 showing a laminar lesion in the upper part of layer VI 204 days after irradi- 

 ation, it is apparent that the laminar lesion is filled with ner\'e fibers that 

 form a dense, abnormal striation, which rather taithtully lollows the undula- 

 tions of the laminar lesion. Fronr a study ot a large amoimt of material (pre- 



FiG. 2. Laminar lesion (1) in the postcentral region of another rabbit 204 days 

 after irradiation. .Almost normal cortical sector at the extreme left of the figure. Peak 

 dose: 27,000 rads : a\'erage dose: 9,000 rads: surface dose: 6,000 rads: number of 

 deuterons per cm': 7.4 X 10''. Formalin fixation, frozen section, Nissl stain, X 50. 



