THE SPINAL, CORD. 383 



and staining preparations, the longitudinal fibres present the appear- 

 ance of minute cylinders cut across ; while those which are horizontal 



FIG. 103. 



TRANSVERSE SECTION OF THE SPINAL CORD IN MAN; lumbar region. 



or oblique are seen in profile for a longer or shorter distance in the 

 section. 



The anterior column, included between the anterior median fissure 

 and the anterior nerve roots, consists in great measure of fibres from 

 the anterior horn of gray substance on the opposite side. The trans- 

 verse band of white substance, at the bottom of the anterior median 

 fissure, is known as the white commissure; but this name is not 

 entirely appropriate, since the fibres in question do not connect corre- 

 sponding parts on the two sides. Those joining the right anterior 

 column come from the gray substance of the left anterior horn ; and 

 those which enter the left anterior column come from the gray sub- 

 stance of the right anterior horn. The so-called white commissure 

 is therefore in reality a decussation, connecting the anterior columns 

 on each side with the gray substance of the opposite side of the cord. 



The lateral column, occupying the space between the anterior and 

 posterior nerve roots, derives its fibres from two sources. First, from 

 the whole external border of the anterior horn and a small part of the 

 posterior horn The mode of origin of these fibres In the gray sub- 

 stance is unknown ; but they pass out from it horizontally and obliquely 

 and then become parallel with the remaining longitudinal fibres of 

 the lateral column. Secondly, from the anterior nerve roots ; some of 

 whose fibres, after traversing the gray substance of the anterior horn, 

 pass out from it in a lateral direction like those just described, and join 

 the lateral column. At each level, therefore, although the great mass 

 of fibres in the lateral column are longitudinal, there are always some 

 which are oblique, emerging from the gray substance, to become longi- 

 tudinal at a higher point. 



