272 NEKVOUS SYSTEM. 



root-fibres, immediately after their entrance into that por- 

 tion of the gray substance which contains a nerve-plexus, 

 is lost in this plexus ; another portion extends farther for- 

 ward, and, in proportion as the fibres pass forward, they 

 likewise take part, by constant divisions, in the formation 

 of the nerve-plexus. This plexus, in which larger and small- 

 er nerve-cells are interspersed as it were as knotted points 

 (Knotenpunkte), are in direct connection with the plexus of 

 the anterior cornua. From these cells nerve-fibres arise, 

 which cross the median line in the gray commissure in front 

 of and behind the central canal, then curve backward, to 

 pass up to the brain, in part in the vertical fasciculi of the 

 posterior cornua, in part in the posterior columns, between 

 both of which numerous connections may exist which are 

 as yet inextricable.' This view involves a complete decus- 

 sation in the spinal cord, through the fibrous elements of 

 the posterior roots passing into this part. Whether this 

 be in reality a complete or a partial decussation in this 

 situation, a part of the fibres arising from the nerve- 

 plexus passing simply backward without crossing the me- 

 dian line, cannot be determined by definite anatomical in- 

 vestigations ; but pathological researches, as well as the 

 experimental results of that most competent observer, 

 Brown-Sequard, are decidedly in favor of a complete decus- 

 sation. 



" Finally, it must be admitted that two points especially 

 are evident : 



u l. In the direction of the nerve-fibres which enter 

 through the posterior roots, the gray substance has more 

 numerous connections than in those which pass to the spi-~ 

 nal cord through the anterior roots. 



" 2. The morphological distinction determinable between 

 the anterior and the posterior roots is, that the former take 

 their origin directly from the nerve-cells by means of the 

 nerve-prolongations, while in the latter, it is only indirect 

 through the nerve-plexus with the protoplasmic prolonga- 



