354 



ANATOMY OF THE CENTEAL NERVOUS SYSTEM. 



columns, "belongs to the tracts of descending degeneration. In the lumbar cord it 

 turns in toward the median septum, and lies close to it, as the "oval field" (Fleehsig). 

 It can be traced into the conus terrainalis. And, while its termination is well 

 known, its beginning is not, it having been traced upward only to the cervical region. 

 For the present it will be well to designate this long tract of very thick fibers as the 

 dorsal cervico-lumbar tract. 



Medulla cervicalis. 



IMudulla lumhalis. 

 Fig. 228. — Compression of the cord at the level of the seventh dorsal nerve. 

 Ascending degeneration to the left, descending in the sections on the right. The 

 products of degeneration stained black with perosmic acid: Marchi's method. 

 (After Hoche.) 



A second portion (3, Kg. 327) of the posterior root-fibers does not turn 

 into the colnmns, but penetrates the white matter by curves^ to lose itself 

 in Clarke's column, where its fibers arborize around the cells of that column. 

 Some of the fibers (3) pass directly across the posterior horn, ventral to 

 the substantia gelatinosa Eolandi, and then course farther in the marginal 

 zone of the lateral column. They are well shown in Pig. 323. 



