THE SPINAL CORD 



841 



well as toward Clarke's column, while a third group of fibres forms the so-called 

 marginal tract, 1 situated close to or among (he entering fibres of the dorsal roots, 

 but frequently described as lying in the lateral column. The tract is demonstrable 

 in all levels and is made up of successive increments of relatively short axones 

 (traversing not more than three or four segments) to end in relation with the cells 

 in the gelatinosa Rolandi. 



Ground Bundle of the Dorsal Column. A zone of fibres contiguous with the 

 jlprsal face of the gray column, and termed the fasciculus dorsalis proprius or dorsal 



D.R 



D.R 



FIG. 613. Ramifications of the central processes (axones) of afferent neurones entering the spinal cord as 

 seen in longitudinal section (schematic) : D.R . Axones of dorsal roots, b. Their bifurcation, clt. Collaterals. 

 t. Telodendria ending in proximity of cells in the gray substance. F.C. Axones of gracile and cuneate fasciculi, 



ground bundle, is composed of axones arising from the smaller cells of the dorsal 

 horn, which, after entering the white substance and bifurcating into ascending 

 and descending branches, come into relation with other levels of the gray column 

 by means of collaterals and terminating in it after a comparatively short course. 

 They are therefore to be regarded purely as association or "longitudinal com- 

 missural" fibres. The dorsal comucommissura^tract^^n/ra/es H inter strangs- 

 bundel [Striimpell]; zone cornucommissurale [Marie]), occupying a triangular 

 interval at the apex of the trans-sected dorsal column, and the septomarginal 

 tract [of Bruce], in apposition with the postseptum, belong to this category of asso- 

 ciation bundles. Both tracts are most evident in the lumbar portion of the cord. 



1 First described by E. C. Spitzka a 885) and Lissauer (1886), and usually bearing the name of the latter. 



