MORPHOLOGICAL EFFECT OF X-RAYS TO THE CNS 227 



grade swelling of the nerve cells another. In approaching this question, it 

 seems necessary to consider the condition of the whole tissue concerned and 

 not solely the nerve cells, since they are only a part of the tissue, and a 

 necrosis of nerve cells alone does not cause tissue disintegration as seen, 

 for example, in anoxic selective neuronal necrosis. Only if the oligoglia 

 and astrocytic glia are also destroyed, does the continuity of the tissue 

 break down. As we ha\e seen in Cajal preparations, astroglia processes 

 show a granular decay rather quickly, long before regressive changes in the 

 vessel walls are demonstrable. Schiimmelfeder (1957) also mentions disap- 

 pearance of ribonucleic acid in glia cells. This would indicate a much more 

 severe lesion of the neivous tissue: however, definite tissue disintegration 

 needs a certain time to become manifest with clear structural changes. In 

 initial stages, when necrosis is not yet clearly apparent, the most reliable 

 histologic phenomenon seems to be the immigration of single leucocytes 

 into the tissue and the beginning of erythrodiapedesis. We have tried to 

 study the earliest stages of cortical necrosis in regard to the function of the 

 hematoencephalic barrier. We did not succeed in staining intravitally with 

 trypan blue during initial stages of spongy tissue transformation (Figs. 

 15-19). when seemingly only minor alterations such as moderate swelling 

 and dissolution of the Nissl substance without significant changes of the 

 nuclei were seen. A positive result was attainable, however, before distinct 

 symptoms of tissue disintegration became e\ident. Thus, the blue staining 

 with trypan blue was complete as soon as single diapedetic hemorrhages of 

 small size in the zone of irradiation could be observed or single polymorpho- 

 nuclear leucocytes had immigrated into the nervous tissue. This is demon- 

 strated by a section stained with the azocarmin Malloiy method of Heiden- 

 hain (Fig. 20) and, for comparison, by a macro photo of the blue stained 

 field on the siufacc of the brain i Fig. 21). 



Discussion 



We must emphasize that the delayed radionecroses of the spinal cord are 

 not significantly diflferent from those in the brain. We obserxe the same 

 phenomena of altered vascular permeability which in the white matter 

 results chiefly in transudation and in the gray matter chiefly in plasmatic 

 infiltration, often with erythrodiapedesis. It now seems established beyond 

 doubt that these processes are primary to all other destruction of nervous 

 tissue in delayed radionecrosis. although in many cases structural changes 

 of the vessels are not evident. The same pathogenic mechanism in delayed 

 radionecrosis is valid in the human brain, as has been demonstrated by 

 Fischer and Holfelder (1933), Markiewicz (1935), Scholz and Hsu (1938), 

 Zeman (1949, 1955) and others. In a necrotic zone, e\'en after many years 



