THE SPINE. 



381 



through the formatio reticularis of the medulla, and 

 making a backward turn through the superior med- 

 ullary velum of the same side. 



Other fibers of this tract have been traced to the 

 corpora quadrigemina, the thalamus, substantia 

 nigra, and the lenticular nucleus of the cerebrum. 

 The fibers of this tract extend the whole length of 



Posterior roof. 



Posterior fissure. 



Lissaur's 

 marginal 

 ground 

 bundle. 



Comma 

 tract. 



Pia mater. 



Direct pyramidal 

 tract. 



A tUerior root of spinal nerve. 



Anterior fissure. 



Fig. 268. Cross section of spinal cord cervical region, i, Zona ter- 

 minalis; 2, zona reticularis; 3, substantia gelatinosa of Rolando; 4, 

 stellate cells of posterior horn; 5, column of Clarke; 6, Waldeyer's cen- 

 tral cell column ; 7, cells of lateral horn; 8, 'central canal; 9, antero-me- 

 ,sial cells; 10,^ postero-mesial cells; n, % antero-lateral cells; 12, postero- 

 lateral cells. 



the cord and probably have "their origin in the cells 

 of the posterior horn. 



3. The crossed pyramidal tract is a large and 

 well-defined bundle that lies just beneath the direct 

 cerebellar; that is, between this and the posterior 

 horn. Below the point where the direct cerebellar 



