164 



PHYSIOLOGY OF CENTRAL NERVOUS SYSTEM. 



movements. On the histological side it has been shown, as stated 

 above, that the fibers, particularly the exogenous fibers, end in 

 nuclei of the medulla and thence are continued forward by the great 

 sensory tract known as the " fillet," to end eventually in that part 

 of the cortex of the cerebrum designated as the area of the body 

 senses. 



Ascending (Afferent or Sensory) Paths in the Lateral 

 Columns. The two best known ascending tracts in these columns 

 are those of Flechsig and of Gowers. The Flechsig bundle or dor- 

 sal cerebellar tract takes its origin in the upper lumbar region, 

 and is composed of axons connected with the tract cells of Clarke's 

 column. The impulses which its fibers convey are brought into 

 the cord through those fibers of the posterior root that end around 

 the cells of Clarke's column. A number of the fibers in this col- 

 umn end doubtless in the gray matter of the upper regions of the 



cord, but most of them con- 

 tinue upward on the same side, 

 enter the inferior peduncle of 

 the cerebellum, and terminate 

 in the posterior and median 

 portions of the vermiform lobe, 

 mainly on the same side, but 

 partly also on the opposite 

 side. The tract of Gowers, 

 situated ventrally to Flechsig's 

 bundle (gr, Fig. 70), may ex- 

 tend forward into the anterior 

 columns along the periphery 

 of the cord. The two bundles 

 may be more or less intermin- 

 gled at the points of contact. 

 This tract begins also in the 

 upper lumbar region, its fibers arising from tract cells on the same 

 side situated in the anterior horn and the intermediate portions of 

 the gray matter. Many of the fibers in this tract doubtless termi- 

 nate in the cord itself, since the bundle does not increase regularly in 

 size as it passes up the cord. Most of the bundle continues forward, 

 however, along the ventral side of the pons, gradually shifts more 

 to the dorsal side, and at the level of the superior peduncles of the 

 cerebellum turns backward, for the most part at least, and passes 

 to the cerebellum by way of the superior peduncles and the valve of 

 Vieussens, to end in the vermiform lobe chiefly on the same side, 

 but to some extent on the opposite side* (Fig. 73). Regarding 



* For the literature upon these tracts see Van Gehuchten, "Le Nevraxe," 

 3, 157, 1901. 



Fig. 73. To show the course of the fibers 

 of the cerebellar tracts of the cord (Mott) : 

 v.a.c. f ventral tract (Gowers) ; d.a.c, dor- 

 sal tract (Flechsig); s.v., superior vermis; 

 P.C.Q., posterior corpora quadrigemina. 



