THE HISTOLOGY OF DISSEMINATED SCLEROSIS. 697 



as the posterior commissure : a further area involves one anterior quadrant of the cord, 

 with the exception of a group of fibres in the angle of the anterior fissure — this area is pos- 

 teriorly surrounded by a faintly-staining zone. At D8 the posterior column area has again 

 diminished in size and is limited to an oval, with indistinct outlines, surrounding the dorsal 

 portion of the posterior median fissure : in both posterior horns a narrow band of demyelinated 

 tissue stretches from the surface to the peri-central tissue ; and a small marginal tri- 

 angular area lies ventral to one posterior horn. At D10 the section is normal except for 

 a narrow band in one posterior horn and a small area continuous with it in the posterior 

 root-entry zone. At D12 the section is also normal, except for a slight peri-central sclerosis 

 and a diffuse and faint staining in the antero -lateral and posterior columns. 



Lumbar Region (figs. 112-113). — With the exception of the outer two-thirds of the 

 posterior columns, the whole section at Ll shows extensive diffuse staining : at L2 the 

 whole transverse section is similarly involved — a triangular area in the one posterior 

 column alone escaping. This faint diffuse staining of the whole cord is continued 

 throughout L3 and L4. 



Medulla Oblongata. — At its lower level (fig. 98) there is a large and dense area of sclerosis 

 present in the region of the substantia gelatinosa Rolandi, which is completely obliterated, 

 together with the descending root of the Vth nerve and the adjacent formatio reticularis 

 fibres. At the middle of the inferior olive (fig. 99) five small areas are present : these He 

 around the central canal, in the substantia gelatinosa Rolandi, in the descending fibres of 

 the Vth nerve, in the gracile nucleus, and on the surface of the pyramid all on the same side. 



Pons Varolii. — A section through the lower portion of the pons shows no marked in- 

 volvement of the peri-ventricular area. One large area, however, extends from the floor 

 of the ventricle as far as the Vllth nucleus : it involves also part of the Vlth nucleus, the 

 fibres of the Vllth nerve during this part of their course, and a small projection reaches 

 as far as the mesial side of the restiform body. A large number of diffuse areas is present 

 in the white matter of the cerebellum : most of these show a central zone of dense sclerosis, 

 and two of these are present in the right dentate nucleus. Several small areas are present 

 in individual folise of the cerebellum. 



Middle Pons. — Sections at this level show few areas : one small patch extends inwards 

 from the surface into the right cerebellar white matter, an early band of sclerosis extends 

 from the ventricular surface into the right dentate nucleus, and the nodule is demyelin- 

 ated. At a higher level the motor nucleus of the Vth nerve on one side is picked out, and 

 still higher a round dense area is present anterior to the end of the right superior cerebellar 

 peduncle. This area extends inwards from the surface and involves part of the lateral fillet 

 and a portion of the fibres of the superior cerebellar peduncle before their decussation. 



Mid-Brain. — The peri-aqueductal tissue is here irregularly involved : on one side the 

 sclerosis affects only the adjoining grey matter, but on the other it spreads out as a tri- 

 angular-shaped area into the white matter and includes a small portion of the anterior Illrd 

 nucleus. The emerging oculo-motor fibres are also involved, and several small areas lie 

 in the crura on one side. The optic chiasma is cut across by an oval-shaped band of sclerosis 

 (fig. 101) not far from the middle fine, and a smaller oval area is found in the remaining 

 substance of the chiasma, an area which in serial section is found continuous with the larger 

 one. The inner aspects of both optic nerves, near the chiasma, are also affected (fig. 100) — 

 the zone of sclerosis being continuous with the anterior margin of the sclerotic band in 

 the chiasma. 



Cerebral Hemispheres.— {\) Horizontal section through the basal ganglia near the base 

 of the optic thalamus (figs. 93-94). The peri-ventricular localisation is in this case again 

 very marked, especially around both posterior horns. These are surrounded by irregular 

 zones of sclerosis, which extend for a varying distance into the adjoining white matter : 

 on the mesial side of both horns this extends into the grey matter at the base of the fissure : 



