NORMAL HISTOLOGY. 



292 



with nerve-fibres, these being principally the cells of the anterior 

 horn, which are continued into the large motor nerves, and the 



FIG. 326. 



PR 



Diagram illustrating the probable relations between the cells and the fibres and the principal tracts 

 of the spinal cord ; the left half of the figure exhibits the communications of the several varieties of 

 nerve-cells : A , f, anterior and posterior cornua of gray matter ; PR, posterior root-bundles ; DP, 

 direct pyramidal tract ; CP, crossed pyramidal tract ; DC, direct cerebellar path ; GB, Gowers's 

 tract ; a, motor cells passing directly into fibres of anterior roots of spinal nerves ; b, various cells of 

 the antero-Iateral column, including elements of Clarke's column (&') and of substantia Rolandi ; 

 some give off collateral branches of remarkable size ; c, commissural cells ; d, cells to posterior 

 column ; e, Golgi cells of posterior horn. The right half of the diagram shows the communications 

 established by means of the collateral fibres. (After Lenhossik.) 



cells which give off fibres passing into and forming part of the 

 anterior and the lateral columns of the cord. The cells of the 

 posterior horn in many cases probably do not connect with nerve- 

 fibres, but bear axis-cylinder processes, which break up into delicate , 

 fibrils confined to the gray matter. It has been shown, on the other 

 hand, that the sensory fibres, after dividing into ascending and 

 descending branches on entering the white matter, give off lateral 

 twigs, which run at right angles to the longitudinal fibres ; on enter- 

 ing the gray matter the horizontal branches divide into tufts of fibrils 

 which end free, often, however, in close relation, but without 

 anatomical continuity, with the nerve-cells. Such terminal sen- 

 sory fibres are especially numerous in Clarke's column and in the 

 substantia gelatinosa, to the formation of whose intricate fibrillar 

 complex they largely contribute. The accompanying diagram, after 



