THE NERVOUS SYSTEM. 413 



:i little inwards, without forming any plexus, or sub-dividing 

 to any considerable extent into subordinate fasciculi, to the 

 innermost portions of the anterior horns, skirting the ante- 

 rior columns. In this course they pass through the inner 

 group of the many rayed, large nerve-cells, in perfectly com- 

 pact bundles, however, and having no connection whatever 

 with the processes of the cells, as may be readily perceived 

 under a strong magnifying power, when the individual nerve- 

 fibres may be traced quite beyond these cells. Now, if these 

 bundles derived from the anterior roots are traced further, it 

 will be perceived, in favorable sections, that they extend to 

 the lateral parts of the anterior commissure, continuing to run 

 in the anterior horns, and, that ultimately, forming more or 

 less Avell-marked curves, they are continuous with its fibres, 

 and in fact are disposed in such a way, that the root-fibres of 

 the right side pass into the left anterior column, and those of 

 the left side into the right. Consequently there is established 

 in the white commissure a connection of the longitudinal fibres 

 of the anterior columns and of a part of the motor roots, 

 together with a total decussation. 



A large number of the fibres of the motor roots take no part 

 in the above-described decussation, and are Avholly unconnected 

 with the anterior fasciculi, — these are the root-fibres which 

 enter the anterior horns the most externally. Forming, for 

 the most part, smaller fasciculi, or even as separate fibres, and 

 therefore less easily observable, they run in part directly 

 backwards, and in part arch outwards, but ultimately bend 

 towards the anterior half of the lateral column, where they 

 pass between the outer groups of the large, many-rayed cells 

 of the anterior horns, and then enter the lateral column in a 

 horizontal direction. These transverse fibres now penetrate 

 to various depths (nearly half, or even more) into the lateral 

 column, then curve upwards, and after running thus a short 

 distance, appear as longitudinal fibres. Consequently, to 

 express the same thing in other words, a second portion of the 

 motor roots arises from the anterior half of the lateral column 

 of the same side, and quits the spinal cord without previously 

 undergoing any decussation. 



It is, moreover, worthy of remark, that most of thff fibres, 

 perhaps all, which join the motor roots from the anterior and 



