THE BEGIONS OF THE SPINAL COED 



485 



protuberance makes its appearance at the base of the anterior 

 horn, on its lateral aspect. This is the precursor of the larger 

 lateral horn of the cervical region. In the upper dorsal region it 

 contains a small cell group, the dorso-lateral. 



The nerve centers of the dorsal segments control the upper 

 abdominal region, the thorax, and the viscera. 



In the lower half of the cervical region the spinal cord presents 

 a distinct enlargement, within the grey matter of which are the 

 nuclei for the upper limbs. The spinal cord in this region is 

 somewhat flattened, its transverse diameter considerably exceeding 

 its antero-posterior. The major portion of the white matter is 

 still contained within its dorsal rather than its ventral portion, 

 the grey commissure appearing to lie somewhat in front of the 

 center. The posterior median septum dips inward for a much 

 greater distance than does the anterior median fissure. 



The posterior columns are decidedly larger than the anterior, 

 and a distinct groove, from which a fibrous septum is continued 



FIG. 380. TRANSECTION OF THE SPINAL CORD OF A CHILD, SEVENTH CERVICAL SEGMENT. 



Weigert stain, x 7. 



inward, separates the postero-internal from the postero-lateral 

 column. 



The dorsal grey horns are long, relatively slender, and more 

 divergent than in the lower levels. They do not reach the sur- 

 face of the spinal cord, but are connected therewith by the long, 

 slender dorsal nerve roots. The grey matter of the dorsal horns 

 in this region is more or less invaded by bundles of nerve fibres 

 derived from the lateral and posterior columns ; the tips of the 



