WHITE MATTER OF THE SPINAL CORD. 305 



in the first instance be traced as a direct continuation 

 from the floor of the fourth ventricle into a minute fun- 

 nel-shaped fissure or line. 



As for the ganglion-cells, they are generally found in 

 the largest number in the anterior and lateral parts of 

 the anterior horns. It is at this spot that we chiefly meet 

 with the large many-rayed corpuscles which we consi- 

 dered the last time corpuscles, which have in great part 

 been traced into efferent nerves of the anterior root, and 

 therefore give origin to motor nerves. 



An analogous, but less distinctly grouped accumulation 

 is found in the direction of the posterior horns, but there 

 the cells are rather the small, many-rayed ones, such as 

 those I lately described to you ; they are connected with 

 the fibres which run into the posterior root, and are 

 therefore probably subservient to the functions of sensa- 

 tion. Besides, there is generally a third, sometimes more 

 closely aggregated, at others more scattered, group of 

 cells to be seen, which in their whole conformation re- 

 mind us of the familiar cell-forms we meet with in the 

 ganglia (Figs. 89, C ; 90, gs'). Their special position in 

 the spinal marrow is certainly not so clearly defined as 

 that of the other parts ; perhaps they should be regarded 

 as the origin of the sympathetic roots which run from the 

 spinal marrow to the main trunk of the sympathetic, but 

 this is as yet by no means clearly made out. 



In the white substance of the anterior, lateral and pos- 

 terior columns are found the medullated nerve-fibres, 

 which in general follow an ascending or descending 

 course, so that in transverse sections of the spinal mar- 

 row we scarcely gain sight of anything else than trans- 

 verse sections of the nerve-fibres. Under the microscope 

 therefore we generally see dark points, every one of 

 which corresponds to a nerve-fibre. The whole mass of 

 fibres constituting the columns of the spinal cord is, from 



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