620 



STRUCTURE OF THE SPINAL CORD 



[CH. XLII. 



excess of neuroglia into a rounded mass called the substantia yelatinosa of Rolando. 

 The cervical cord is wider from side to side than from before back ; this is owing 

 to the great width of the lateral columns. 



In the dorsal region the grey matter bears only a small proportion to the white, 

 and the posterior roots in particular run a long course through the white matter after 

 they enter the cord ; the grey commissure is thinner and narrower than in the 

 cervical region. The intermedio-lateral tract is here most marked, and forms a 



FIG. 452. The above diagrams are reproductions of photo-micrographs from the spinal cord of a monkey, 

 in which the operation of left hemisection had been performed some weeks previously (Mott.) The 

 sections were stained by Weigert's method, by which the grey matter is bleached, while the healthy 

 white matter remains dark blue. The degenerated tracts are also bleached. A is a section of the 

 cord in the thoracic region below the lesion ; the crossed pyramidal tract is degenerated. B is a 

 section lower down in the lumbar enlargement ; the degenerated pyramidal tract is now smaller. 

 C is a section in the thoracic region some little distance above the lesion. The degenerated tracts 

 seen are in the outer part of Coil's column, and in the direct cerebellar tract. D is a section higher 

 up in the cervical region ; the degeneration in Goll's column now occupies a median position ; the 

 degenerations in the direct cerebellar tract, and in the tract of Gowers, are also well shown. Notice 

 that in all cases the degenerated traces are on the same side as the injury. 



prominence often called the lateral horn. This is shown in fig. 452 C. Clarke's 

 column is also confined to this region of the cord. 



In the lumbar enlargement the grey matter again bears a very large proportion 

 to the whole size of the transverse section, but its posterior cornua are snorter and 

 blunter than they are in the cervical region. The grey commissure is short and 

 extremely narrow. The cord is circular on transverse section. 



At the upper part of the conns medullaris^ which is the portion of the cord im- 

 mediately below the lumbar enlargement, the grey substance occupies nearly the 

 whole of the transverse section, as it is only invested by a thin layer of white sub- 



