MORPHOLOGICAL EFFECT OF X-RAYS TO THE CNS 



213 



caused by destruction of tissue. The remarkable fact is the sharply limited 

 blue stainino' of the whole gray matter, which demonstrates no disintegration 

 at all. 



These investigations have been continued in 21 additional adult rabbits. 

 Equivalent changes in the spinal cord could be produced using the same 

 technique with fractionated doses totaling 3,000 r. No exact relation between 

 the amount of applied r and the length of the interval can be stated, but on 

 the average the intervals became longer with diminution of the total dose. 

 The minimum single dose sufficient to produce severe changes in the cord 

 after 5 months was 2.000 r. Some figines demonstrating the pathologic 

 findings in this material show again the important role which the breakdown 

 of the blood-brain barrier plays in the pathogenesis of changes in the 

 nervous tissue. Thus we see in Fig. 2 that the numerous focal changes in 

 the white matter follow the distribution of the small arteries entering the 

 cord from the vasocorona. In this case, a single dose of 3,500 r was followed 

 by paralysis 15 weeks later. Two small vessels in the white matter (Fig. 3) 



Fig. 2. Delayed lesion of the spinal cord of a rabbit, 3% months after a local 

 single x-ray dose of 3,500 r. Numerous areas of disintegration in the white matter fol- 

 low the radial direction of the entering vessels of the vasocorona. Myelin stain 

 (Schroder). 



show a swelling and disintegration of their walls cau.sed by infiltration with 

 a plasmatic material which is stained yellow in van Gieson preparations. 



