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MANUAL OF HISTOLOGY. 



are remarkable for their small diameter, as compared with their fellows 

 situated more externally. One spot in particular presents very fine fibres, 

 namely, close to the inner angle of the lateral column, where the anterior 

 and posterior cornua meet. 



Very characteristic differences in diameter are also apparent, if we com- 

 pare the chief masses of fibres of the various columns. The anterior (/) 

 possess the broadest, and consist principally of such. Those bundles of the 

 lateral column in the vicinity of the grey matter are made up of very fine 



elements. Further out to wards 

 the periphery a stronger series 

 is to be found occurring with 

 great regularity (m), and in- 

 termixed more externally still 

 with small fasciculi of finer 

 fi brillae. The fibres of the pos- 

 terior column, compared with 

 those of the anterior, are dis- 

 tinctly smaller in diameter. 

 But in the bands of Goll we 

 meet with the most delicate 

 filaments of all disposed with 

 the utmost regularity. 



Let us now turn to the 

 transverse and oblique sys- 

 tems of fibres coursing through 

 the white columns. 



These, without counting 

 the elements of the two com- 

 missures, consist of the root- 

 bundles of the spinal nerves 

 (i, k) emerging from the grey 

 cornua, and intersecting the 

 longitudinal bands of fibres 

 of the white substance. But 

 it is only the posterior sys- 

 tems of fasciculi that run 

 really horizontally, the motor root-bundles take an oblique course. 



The anterior or motor roots pass through the white substance in several 

 fasciculi, and with a tolerably straight course, separating the anterior from 

 the lateral columns. In this way they arrive at the anterior cornu still 

 in the form of broad fibres, and then break up into delicate elements, 

 which radiate in all directions, and in various planes, forming at the same 

 time numerous loops. Many take their course along the surface of the cornu 

 inwards, in an arch towards the anterior longitudinal fissure. Others, 

 again, are directed outwards towards the boundary of the lateral column, 

 turning round again and running inwards. Other bundles, again, may be 

 followed directly backwards as far as the base of the posterior cornu. 



In order the better to understand their further destiny, let us accom- 

 pany these nervous fasciculi into the anterior cornu, and in the very first 

 place inquire into the complicated structure of the grey matter. ' 



In the delicate spongy mass, of which its sustentacular tissue is com- 

 posed, we see, in the first place, an inextricable maze of fine and extremely 

 delicate nerve filaments. Then, in the anterior cornu large multipolar 



Fig. 557. Transverse section through the under half of the 

 human cord (after Deiters). a, central canal ; 6, anterior; 

 c, posterior fissure; d, anterior cornu, with large ganglion 

 cells; e, posterior cornu with smaller; /, anterior white 

 commissure; g, sustentacular substance around the cen- 

 tral canal; h, posterior grey commissure; i, bundles of 

 the anterior, and k, of the posterior spinal nerve roots; 

 I, anterior; m, lateral; n, posterior column. 



