540 S. WALTER HANSON 



lateral part of the dorsal root. The medial part, approxmiately 

 half, is stained very lightly and contains only a small part of the 

 axons that are normally present. The illustration represents 

 as high a degree of degeneration as was seen in any of the prepara- 

 tions. It was in the middle of a degeneration involving three 

 segments, and was drawn from the fifth Imnbar segment of Cat 

 II in which the fourth, fifth, and sixth lumbar roots were ligated. 

 The degeneration was at its maxunmn in the fifth Imnbar segment 

 and decreased in an upward and downward direction. There 

 was no clear evidence of degeneration in the third Imnbar seg- 

 ment. In the highest part of the fourth lumbar segment a slight 

 degeneration was evident. It gradually became m.ore pro- 

 nounced as the series was followed downward through this seg- 

 ment. Throughout the fifth lumbar segment the degeneration 

 was well marked, and gradually decreased as one passed down- 

 ward through the series of the sixth Imnbar segment. No degen- 

 eration could be seen in the seventh Imnbar segment. These 

 facts show that the non-medullated fibers are chiefly confined to 

 the segment at which they enter the cord. They do, however, 

 extend up and down to some extent, as is shown by the fact that 

 the degeneration was greater in the fifth than in the fourth or 

 sixth lum.bar segments. From what was seen in Pal-Weigert 

 and Marchi preparations it is clear that some m.edullated axons 

 must have degenerated and disappeared from the third and 

 seventh lumbar segments, but their absence can not be detected 

 in pyridine-silver preparations. It is also probable that some 

 few non-medullated axons have disappeared from these segments 

 without bringing the total loss of axons to an amount appreciable 

 by the method used. Even where the degeneration is at its 



Fig. 4 Outline drawing to show the location from which figure 5 was drawn. 

 c.p., columna posterior; s.g.R., substantia gelatinosa Rolandi; f.c, fasciculus 

 cuneatus; L.t., Lissauer's tract; L.t'., isolated portion of Lissauer's tract; r.p., 

 radix posterior. 



Fig. 5 From the fifth lumbar segment of the spinal cord of a cat, killed 24 

 days after the unilateral ligation of the fourth, fifth, and sixth lumbar roots. 

 For orientation see figure 4. Notice the degeneration in the medial half of Lis- 

 sauer's tract and in the entering root and cuneate fasciculus. Pyridine-silvcr. 

 X 167. 



