MORPHOLOGICAL EFFECT OF X-RAYS TO THE CNS 225 



slight pallor in the cortex (Fio. 18) . Hii^h power demonstrates disappearance 

 of Nissl bodies in the large pyramidal cells so that the perikaryon is generally 

 pale and difTusely stained, whereas the nuclei of the smaller nerve cells 

 contain rather coarse chromatin particles (Fig. 19). It is extremely difficult 

 to judge the whole tissue situation from deviations in appearance of the 

 cortical nerve cells alone. The significance of such deviations seems to re- 

 c}uire a special cell study as performed by Krogh and Bergeder ( 1957) using 

 the o^allocvanin stain of Einarson and bv Schiimmelfeder (1957) in his 





.^. «•'■.,• rii.'.t.i...'' i. ■,.■>•- * -.,', ,' , ••• '.•,•- • J, ■<'■■■ ;- ■'' : t -* '. .<- 



>• •'*..;» ";•^ i-v/vV.".".?.' is ':..'.■- •- > -,• '■ „ :• . .. .... ■■.;.-•".'*, ' '/^•'.■' h-.,' x'-'^ • ' 



Fig. 18. EquivaK-nt of the spongy region in Fig. 17, stained with the gallocyanin 

 method. In this zone, the cells appear less stained. 



histochemical investigations with fluorescent acridin-orange on the nerve 

 cells of the cerebellar cortex. With regard to the different types of nerve 

 cell changes after irradiation of 5,000 to 20.000 r, they made similar obser- 

 vations on cortical nerve cells, and they considered this to be an expression 

 of cell necrosis. Certainly, it requires a high level of experience to decide 

 from the appearance of the cell alone that cell shrinking with dark staining 

 of the perikaryon and a pyknotic nucleus is not reversible and must inev- 

 itably lead to necrosis. In cresyl \iolet and gallocyanin preparations, we 

 have seen such cells distributed over wide regions including the cortex of 

 control animals which had ne\er been irradiated. Their significance is not 



