26 THE SPINAL CORD. 



pyramidal tract (where it is most strongly marked) round the superficial part of the 

 lateral column in front of the dorso-lateral cerebellar tract, and tailing off gradually 

 between the issuing anterior roots to reach the anterior column. It can be traced 

 upwards into the medulla oblongata and pons Varolii (fig. 27), and eventually enters 

 the cerebellum along with the superior peduncle, passing mainly to the vermis. It is 

 uncertain from what cells the axis-cylinders of its constituent fibres spring, but it 

 is probable that they arise from some of the cells of the posterior horn. Its fibres 

 are intermingled with those of the descending cerebellar tract. 



The remainder of the antero-lateral column which is not comprised in the above 

 tracts encircles the anterior cornu ; it is termed the antero-lateral ground-bundle. 

 It varies in sectional area with the size of the nerve-roots and of the grey matter, 

 and many of its fibres not improbably are of a commissural nature, serving to 

 connect the grey matter of different segments of the cord. It receives fibres also 

 from the grey matter of the other side through the anterior commissure (fig. 15, B, 

 a.c.), and is in part composed of fibres of the anterior roots which course for a 

 certain distance obliquely within it before leaving the cord. Many intersegmental 

 fibres also occur scattered amongst the fibres of the long tracts. 



Tract of Lissauer. At the posterior part of the lateral column, close to the 

 entering fibres of the posterior roots and directly derived from them, there is 

 constantly to be seen a well-marked bundle of fine nerve-fibres, which was first 

 described by Lissauer, and since by Bechterew and others. It is not always confined 

 to the lateral column, but may extend into the postero-lateral column. 



Tracts of the posterior white column. This column is mainly composed 

 of two long ascending tracts, viz., the tract of Goll, which about corresponds with 

 the postero-mesial column, and the tract of Burdach, which embraces the remainder 

 of the posterior column. In the lower part of the cord these two tracts are not 

 marked off from one another in the adult, but from the middle of the dorsal region 

 upwards the postero-mesial column is separated from the postero-lateral by a septum 

 of pia mater. Of the two parts of the posterior column the tract of Burdach is 

 mainly composed of rather large fibres which are joined by, i.e., are continuous with, 

 the large fibres of the entering posterior roots. After a certain course, in which they 

 give off numerous collaterals to the grey matter, they appear to enter the grey matter 

 and to come into intimate relationship, although not into actual continuity, with its 

 cells, especially those of Clarke's column. The fibres of the tract of Goll, on the 

 other hand, are for the most part of smaller diameter. They also are derived from 

 posterior root-fibres, but instead of soon entering the grey matter of the cord many 

 of them run up the postero-mesial column into the medulla oblongata, where they 

 terminate amongst the cells of the nucleus gracilis. 



The column of Goll in the embryo shows a distinction into two parts, one mesial, close to 

 the posterior median fissure, and a dorso-lateral part, lying near the dorsal surface of the cord 

 (Flechsig). 



Descending fibres of the posterior column. In the middle of the 

 sectional area of the postero-lateral column a few fibres are constantly found, 

 which undergo descending degeneration after lesions of the cord. These are often 

 described as constituting a special tract (" comma " tract), but they are a good deal 

 intermingled with fibres of the adjacent ascending tracts. Whether they originate 

 from cells higher up in -the cord or are derived from the descending branches 

 of the posterior root-fibres is uncertain. The latter, it may be remembered, extend 

 a certain distance down the cord from the Y-shaped division of those fibres, giving 

 off collaterals to the grey matter, and ultimately themselves turning into the grey 

 matter. The extent to which these descending branches of the posterior roots may 

 pass down the cord has not as yet been determined. 



