THE HISTOLOGY OF DISSEMINATED SCLEROSIS. 719 



one another across the base of the fissure, and involve both commissures, the base of the 

 posterior horns, and the lateral horns. 



Lumbar Region (figs. 233-236). — At the level of the first segment the picture is very similar 

 to that found throughout the whole dorsal cord, but throughout the remainder of the lumbar 

 and in the sacral cord the areas found are denser and more defined in outline. At L2 a 

 peri-central sclerosis passes into the associated grey matter on either side and affects both 

 commissures : a triangular area extends along the posterior median fissure : smaller areas 

 occur in each' substantia gelatinosa Rolandi, and on the surface of the cord, especially at 

 the tips of the anterior fissure ; and a small area is confined to the postero-lateral grey 

 matter of the anterior horn on one side, with the immediately adjoining nerve fibres. At 

 L3 little change has occurred : the posterior area is now limited to a narrow zone along the 

 fissure, and the area in anterior grey matter is almost continuous with surface areas in the 

 region of the root-emergent zones. At L4 these areas have fused laterally, and the portion 

 within the grey matter involves both postero-lateral and antero-lateral groups of cells. 

 Minute early areas are found along the antero-lateral surface of the opposite side, and 

 the areas around the central canal in the substantia gelatinosa are more extensive. 



At L5 the sclerosis is limited to these three latter areas : they are now still more extensive 

 and involve almost the whole posterior horn on one side and, on the other, the area is con- 

 tinuous with a large glious zone in one extra-medullary posterior root. The sides of the 

 anterior fissure and the posterior columns stain faintly. 



Sacral Region (figs. 237-239). — At Si the peri-central sclerosis extends into the bases 

 of the anterior horns and along each side of the anterior fissure : the areas in the substantia 

 gelatinosa Rolandi are small : a minute area is still present in the postero-lateral group 

 of nerve cells in the anterior horn on each side ; there is also a slight involvement of the 

 fibres around the dorsal portion of the posterior median fissure. At S3 there is almost 

 a complete transection of the cord : a few normal fibres are left around the postero-lateral 

 and anterior margins of the cord. In S4 the normal fibres are limited to a crescentic band 

 lying in the anterior and antero-lateral surfaces, and to a few individual fibres in the regions 

 of the posterior horns. The nerve roots of the cauda equina stain almost normally : a 

 few nerve roots, however, are faintly stained. 



Medulla Oblongata. — At the level of the decussation of the pyramids (fig. 218), two areas 

 of sclerosis are present : the smaller involves one substantia gelatinosa Rolandi ; the larger 

 affects nearly the opposite half of the medulla and extends obliquely from the substantia 

 gelatinosa Rolandi across the central canal to the outer margin of the opposite pyramid. 

 The area ventral to this oblique line is demyelinated, except a few peripheral fibres and 

 pyramidal fibres after or during their decussation. A diffuse change is present throughout 

 much of the remaining tissue. As the large area is traced upwards (fig. 219) it becomes 

 more symmetrical and triangular in shape : its apex lies in the posterior median fissure, 

 almost all the pyramidal fibres are involved, and from the lateral borders projections pass 

 into each gelatinous Rolandic substance. At the level of the decussation of the fillet (fig. 

 220) two clearly-marked areas are present : the one, peri-central, resembles a maple-leaf 

 in form, and includes at its margin the hypoglossal nuclei ; the other is obviously a continua- 

 tion upwards of the previously described triangular area. It now extends from the posterior 

 longitudinal fasciculus and involves both mesial fillets, both pyramids, and the lower end of 

 both inferior olives. 



Middle Medulla. — Few areas are present at this level : the most marked is situated ven- 

 trally in the middle line just at the junction of the mesial fillet with the pyramids. It 

 involves the mesial portion of each pyramid, with a few of the adjoining fillet fibres, and 

 probably represents the continuation upwards of the triangular area. A slight involvement 

 of the tissue along the floor of the IVth ventricle is also present. 



Upper Medulla (fig. 221). — A broad band on one side passes diagonally backwards 



