SENSORY PATHS IN THE CORD 245 



pass from the anterior nerve roots directly into the pyramidal 

 tracts without being interrupted by motor cells. 



The column of Turck and the crossed pyramidal tract are, 

 therefore, the motor paths in the cord. 



Fibers entering the cord by the posterior roots send prolonga- 

 tions both upward and downward in the gray matter of the cord, 

 and communicate by end arborizations with the small sensory 

 cells in the posterior cornua and with cells in several other 

 localities. (See Figs. 77, 84.) Reference to Fig. 77 will show 

 that the connection of the anterior nerve fibers with the gray 

 matter of the cord is simple, while that of the posterior is com- 

 paratively complex, i, 2, 3, 4 are anterior horn cells. Each of 

 these gives rise to an efferent fiber, one of which (A ) is shown 

 distributed to a muscle (M). Each of these cells also is sur- 

 rounded by the end arborization of a fiber (P) from the cortex. 



A fiber from the posterior root is also shown. It originates 

 in a cell of the sensory ganglion (G). It bifurcates, one branch 

 going to the surface (S), the other enters the cord and itself bi- 

 furcates. The branch (E) is short and arborizes around a small 

 cell (Pj) in the posterior cornu, from which a new axis cylinder 

 arises to arborize around the anterior horn cell (4) . The other 

 branch (D) travels upward in the posterior column of the cord. 

 A collateral (5) is seen going to the anterior horn cell (2), one to 

 the posterior horn cell (P 2 ) and another to a cell (C) in the 

 inner base of the posterior cornu (in Clarke's column); from 

 C an axis cylinder enters the direct cerebellar tract. The 

 main fiber (8) may terminate in the gray matter of the cord 

 above, or in the medulla. Impressions brought thus to the 

 cord are carried to the opposite side and pass up through the 

 gray matter in most part. The fibers decussate at no particular 

 point, but throughout the length of the cord. However, some 

 fibers bearing sensory impressions pass to the column of Goll 

 and thus upward, while some also go to the encephalon by the 

 direct cerebellar fasciculi and the columns of Burdach. Ex- 



