THE HISTOLOGY OF DISSEMINATED SCLEEOSIS. 701 



the anterior median fissure on both sides, and in the white matter between the tip of the 

 right anterior horn and the periphery. In the third segment the pyramidal involvement 

 is scarcely recognisable. The posterior columns, near to the central canal, show early 

 change ; and a dense area is found along the left side of the anterior median fissure — 

 extending to meet the area around the central canal and sending a projection into the 

 grey matter of the posterior horn. In the fifth segment the central canal shows a slight 

 ring of sclerosis, and evidence of early involvement is found along each side of the anterior 

 median fissure. 



Sacral Region (figs. 139-142). — In the first and second segments the change is limited 

 to slight involvement of the lateral column on one side, but the third segment shows an 

 almost complete sclerosis of the cord at this level — the only fibres escaping being a few 

 peripheral, symmetrically-situated, antero -lateral and posterior fibres. The fourth sacral 

 segment shows again little change — a small area being present around the central canal 

 and at the tip of the left posterior horn. The nerve roots of the cauda equina are normal. 



Medulla. — Just above the decussation of the pyramids. A quadrilateral area extends 

 round the central canal : from one corner of this a large irregular patch passes to the 

 anterior surface along the middle line, cutting through the middle of the decussation. At 

 a slightly higher level (fig. 118) the central canal sclerosis is still well marked, but it is separated 

 from the adjoining area, which occupies now the position of the left pyramid — leaving only 

 a few superficial fibres intact. This portion, as it is traced upwards, diminishes in size and 

 disappears altogether (fig. 119). The patch around the central canal is still present, together 

 with a small elongated area in the right mesial fillet parallel to the median raphe. Small 

 symmetrical areas are found in the outer arm of the accessory inferior olive on each side — 

 limited to the grey matter of the nucleus. 



Middle Medulla. — An isolated area is present between the right pyramid and the adjoin- 

 ing part of the inferior olive. This affects slightly the right pyramid and intersects the 

 fibres of the hypoglossal nerve. A smaller area is found in a similar position on the opposite 

 side. At a slightly higher level these areas disappear and only one patch is present, involv- 

 ing the right restiform body. This area, when traced upwards, becomes much larger and 

 extends forwards along the surface almost as far as the level of the inferior olive (fig. 120). 

 A similar area appears in the opposite restiform body and this, when traced upwards, is 

 found to reach the angle of the ventricle. 



Upper Medulla. — The floor of the ventricle is here normal. A " shadow " area extends 

 from the angle of the ventricle on one side to the surface of the medulla, and two older areas 

 are found in the same position on the opposite side — separated from each other by normal 

 fibres and unconnected with the ventricle. The left mesial fillet is almost completely obli- 

 terated by an area which extends across the raphe into the opposite olive and part of 

 the pyramidal tract. The left olive contains two areas, one between the olive and the 

 pyramid and the other immediately dorsal to the olive. Several smaller areas occur in 

 the formatio reticularis. 



At the extreme upper limit of the medulla (fig. 121) a dense irregular area extends from 

 the ventricle to the surface, obliterating altogether the restiform body and extending into 

 the white matter of the cerebellum, and surrounded more or less by diffuse " shadow " 

 areas. On the opposite side a diffuse, irregular area extends from the angle of the ventricle 

 into the white matter of the cerebellum. On both sides the peduncle of the flocculus and 

 the intra-medullary portion of the Vlllth nerve are involved. An early area is found also 

 in the hilum of the right dentate nucleus. 



Pons Varolii. — Lower Third. — A dense area extends along the floor of the ventricle from 

 the median raphe to the angles : this is surrounded by a more diffuse sclerosis. An area 

 of dense sclerosis is found along the middle third of the raphe, and here also is found a sur- 

 rounding zone of lighter staining. Both facial nuclei and part of the fibres of each facial 



TRANS. ROY. SOC. EDIN., VOL. L, PART III (NO. 18). 97 



