SPINAL CORD. 



107 



posed of long and short commissu 

 segments of the spinal cord. 



Structure of the Gray 

 Matter. The gray matter, ar- 

 ranged in the form of two 

 crescents, presents an anterior 

 and posterior horn. It is made 

 up of a delicate network of 

 fine nerve fibres (axis cylinders) ? 

 supported by a connective tissue 

 framework of nucleated nerve 

 cells, which in the anterior horns 

 are large and multipolar, and 

 connected with the anterior roots 

 of spinal nerves ; in the posterior 

 horns the nerve cells are smaller, 

 and situated along the inner mar- 

 gin, and in the caput cormi. Small 

 cells are also found in the pos- 

 terior vesicular columns, and in 

 the intermediary lateral tract. 



ral fibres which connect together different 

 FIG. 10. 



a b 



h. 



Scheme of the conducting paths in the spinal 

 cord at the 3d dorsal nerve. The black part 

 is the gray matter, v, anterior, h, w, pos- 

 terior, root; a, direct, and g, crossed, pyra- 

 midal tracts ; b, anterior column, ground 

 bundle ; c, Coil's column ; d, postero-exter- 

 nal column ; e and f, mixed lateral paths ; h, 

 direct cerebellar tracts {Landois). 



COURSE OF THE ANTERIOR AND POSTERIOR ROOTS. 



The Anterior Roots pass through the anterior columns, horizontally, 

 in straight -and distinct bundles, and enter the anterior cornuae, where they 

 diverge in four directions, (i) Many become connected with the prolon- 

 gations of the multipolar nerve cells. (2) Others leave the gray matter, 

 pass through the anterior white commissure, and enter the anterior columns 

 of the opposite side. (3) A considerable number enter the lateral columns 

 of the same side, through which they pass to the medulla oblongata, where 

 they decussate and finally terminate in the corpus striatum of the opposite 

 side. (4) Others traverse the gray matter horizontally, and come into 

 relation with the posterior roots. 



The Posterior Roots enter the posterior horns of the gray matter (i) 

 through the substantia gelatinosa, (2) through the posterior columns ; of 

 the former, some bend upward and downward, and become connected 

 with the anterior cornuse ; others pass through the posterior commissure to 

 the opposite side ; of the latter, fibres pass into the gray matter, to the 

 posterior vesicular columns, passing obliquely through the posterior white 

 columns upward and downward for some distance, and enter the gray 

 matter at different heights. 



