LOCAL IRRADIATION OF CNS WITH HIGH ENERGY PROTONS 347 



were oiven chloralhydrate by a stomach tube, and later on, nembutal anes- 

 thesia was inducted intravenously. The goats were killed 1 to 4 months after 

 irradiation by decapitation under nembutal anesthesia. 



Spinal cords and brains were fixed in 5^? neutral formal-saline. From the 

 irradiated part and adjacent regions of the cord, longitudinal and serial sec- 

 tions were cut in a frontal plane. The rabbit brains were cut sagittally, and 

 the slices were embedded in paraffin or cut in the frozen state. The goat 

 brains were cut horizontally in slices about 5 mm thick and examined macro- 

 scopically. The target region was embedded in celloidin and cut by serial 

 sectioning. The principal staining methods used were hematoxylin and van 

 Gieson's mixture, phosphotungstic acid hematoxylin, Heidenhain's modified 

 Mallory stain for collagen, thionin. Grosthionin and Palmgren's silver impreg- 

 nation for axons. Loyez and Heidenhain's myelin sheath stains, and Ranke's 

 Victoria blue for astrocytes. In a few cases, supplementary stains for demon- 

 stration of iron and fat were used. 



Results 



/' 



Transection of the Spinal CIord 



Eight rabbits were exposed to a single dose of 20 krad with a 1.5 mm beam. 

 The first neiu'ologic symptoms, consisting of lively tendon reflexes in the 

 hind legs and slight knee and ankle clonus, appeared about 8 days after irra- 

 diation: later, flaccid paralysis developed. In the meninges and cord, a band 

 of grayish discoloration 2 mm wide marked the radiated portion of the cord. 

 No hemorrhages or inflammatory signs were visible to the naked eye. Micro- 

 scopic examination revealed a narrow and sharply delimited necrotic zone 

 corresponding to the path of the beam ( Fig. 1 ) . The lesion was broader in 

 the white substance and had about the same breadth as the proton beam. 

 The damaged gray matter was only about half the breadth of the beam 

 (no correction for shrinkage due to fixation was made). In the path of the 

 beam, nerve cells, axons, myelin sheaths, and glial cells were necrotized. No 

 evidence of selecti\e radiation effect on the various components of the neural 

 tissue was seen. Minimal hemorrhages surrounding capillaries and venules 

 were observed at the margin and sometimes in the middle ot the irradiated 

 zone. Large hemorrhages were never seen. Nuclear fragments, slight prolif- 

 eration of astrocytes with bulky cytoplasm, and a few macrophages were 

 noted in a small marginal zone between the irradiated and nonirradiated tis- 

 sue (Fig. 2). Occasional nerve cells adjacent to the irradiated zone were 

 degenerated, others being rather well preserved. In the white substance, the 

 marginal zone was characterized by degenerating axons and myelin sheaths. 

 Iron pigment occurred in a few glial cells at the edge of the necrosis. Fat 



