THE NERVOUS SYSTEM. 



211 



In the posterior column two tracts are recognized: 

 the fasciculus of Goll, occupying the mesal third of the 

 column, and the fasciculus of Bur- 

 dach, composing the remainder. In 

 the medulla of the cat these two 

 tracts may be distinguished by the 

 unaided eye (Fig. 93). They are 

 here called the funiculi of Goll and 

 Burdach, or funiculi gracilis and 

 cuneatus. Their fibers are largely, 

 if not entirely, the axis-cylinder 

 processes of the ganglion cells on 

 the posterior roots of the spinal 

 nerves. They terminate in the nu- 

 clei gracilis and cuneatus, two small 

 masses of nerve cells in the medulla 

 laterad of the fourth ventricle (Fig. 

 98) . That these fibers are processes 

 of the spinal ganglion cells is proved 

 by the fact that they degenerate 

 if the posterior nerve roots are 

 severed close to the cord. In 

 whales, where the pelvic extremi- 

 ties are wanting, the fasciculi of 

 Goll and Burdach are very small. 



The lateral column is composed 

 of five tracts : the direct cerebellar 

 tract, the antero-lateral descending 

 cerebellar tract, the antero-lateral 

 ascending cerebellar tract or Gow- 

 ers's tract, the lateral ground bun- 

 dle, and the crossed pyramidal tract. 



The direct cerebellar tract occupies the superficial re- 

 gion of the cord laterad of the posterior cornu of gray 



FIG. 99. - - DIAGRAM OF 

 SOME FIBER TRACTS. 

 DORSAL ASPECT. 



a/, Antero-lateral ascend- 

 ing cerebellar tract; c, 

 posterior corpus quad- 

 rigeminum; cer, lateral 

 lobe of cerebellum, 

 whose median portion 

 is removed ; eg, the two 

 fasciculi of Goll and 

 Burdach represented as 

 one; cp, crossed pyra- 

 midal or chief motor 

 tract; cp' , crossed pyra- 

 midal tract in the region 

 of the cerebral pedun- 

 cle ; dc, direct cerebellar 

 tract; fi, the large part 

 of the fillet derived from 

 tic: nc, nuclei gracilis 

 and cuneatus ; s, decus- 

 sation of pyramidal 

 tracts; x, sensory or 

 superior pyramidal de- 

 cussation; sp, superior 

 peduncle of cerebel- 

 lum. 



