DEGENERATIONS OF THE CORD. 



429 



THE CORD. 



HEMORRHAGE. 



Hemorrhage is of much less frequent occurrence and much 

 less extensive the clot generally not more than one centi- 

 metre in diameter than in the brain. The condition is 

 generally the result of trauma, though it may occur sponta- 

 neously. When the central canal of the cord is dilated and 

 filled with blood the term hcematomyelia is employed. 



DEGENERATIONS. 



FIG. 198. Secondary degenerations occur 



in the brain and cord as the 

 result of any lesion interrupting 

 the course of nerve-fibres in the 

 brain, cord itself, or posterior 

 nerve-roots. These changes are 

 supposed to be due to the re- 

 moval of normal trophic influ- 

 ences arising in the ganglion- 

 cells from which the nerve-fibres 

 are cut off. The result is the 

 destruction of the medullary 

 sheaths of the fibres, to which is 

 due their opaque white appear- 

 ance. Tracts in the cord so 



FIG. 199. 



Descending degeneration in the pyr- 

 amidal tract following hemorrhage 

 into the internal capsule. The di- 

 rect tract is marked, and is repre- 

 sented at a lower level than it is 

 usually seen (F. W. Mott). 



The ascending tracts of degeneration in 

 the cervical enlargement after experi- 

 mental hemisection of the spinal cord 

 in the mid-dorsal region. The section 

 shows well-marked degeneration of 

 Goll's column, of the direct cerebellar 

 tract, and of the antero-lateral tracts on 

 the same side as the lesion (F. W. Mott). 



