MORPHOLOGICAL EFFECT OF X-RAYS TO THE CNS 221 



Fig. 12. Intravital trypan blue staining of the necrotic region of the same brain as 

 in Fig. 11. 



even when small, was surrounded by a broad shell of sponoy tissue where 

 the cellular elements showed only minor chanoes. To demonstrate the bar- 

 rier function, a series of animals recei\ed a subcutaneous injection of 1 cc 

 of Kr trypan blue solution from 1 to 6 hours after irradiation. As is well 

 known, the brain remains unstained under normal conditions. With disinte- 

 gration of tissue and destruction of vessels, the dye may enter the tissue. 

 Figure 1 1 demonstrates such a necrotic zone which had developed within 

 6 days after x-irradiation with 10,000 r and which involves the whole 

 thickness of the cerebral cortex. From the numerous hemorrhages in the 

 necrotic zone, trypan blue spread diffusely all through the destroyed tissue 

 (Fig. 12) . These cases do not ser\e to illustrate a disrupted barrier function 

 unless the blue staining siupasses the necrosis and extends to the surrounding 

 spongy area where only minor cellular changes are seen. This could be 

 obsened in some cases, but it is difficult to demonstrate. 



Bv shortening the sur\i\al time of the animals, we attempted to observe 

 the earliest stages of tissue necroses. A standard x-ray dose of 20.000 r was 

 applied within 10 min 36 sec. This dose proved sufficient to produce clear 

 necrosis within 24 horns. Surprisinyly. we could produce lesions ot similar 

 size with a considerable diminution of the x-ray dose. After 24 to 26 hours, 

 a large semicircular zone of obvious necrosis covering the irradiated field 

 could be seen extending from the dorsal surface of the cerebral cortex to 

 the corpus callosum. With shorter survival times and in older animals, the 

 depth of the necrotic area flattened (Fig. 13). Here again, a sponginess of 



