706 I)R JAMES W. DAWSON ON 



in the anterolateral columns. In the mid-dorsal region the areas are very irregular in 

 outline, and nearly all radiate as narrow or broad tongue-like projections from the central 

 canal. The base of both anterior horns is thus involved, together with the whole of the 

 lateral horns and the greater part of each posterior horn. The anterior half of both pos- 

 terior columns is also affected, and from this sclerosis, on one side, a dense band runs across 

 the posterior root-entry zone to the surface — extending forwards to involve the fibres of 

 Lissauer's tract. A small isolated area is present also in the antero -lateral column of this 

 side. In the lower dorsal cord one large area is present : it occupies the whole of one antero- 

 lateral column, except a narrow marginal zone, together with the anterior, lateral, and post- 

 erior grey matter and part of the posterior columns on the same side. A small isolated 

 area is present in the opposite anterolateral column. 



Lumbosacral Region (figs. 153-155). — In the second lumbo-sacral segment a large irre- 

 gular area, with diffuse changes at its borders, extends from the central canal to the surface 

 of the cord on one side. Its position is roughly that of the area in the segment just described, 

 but it does not pass so far anteriorly and posteriorly. In L3 this area is still present with a 

 wider extension and faintly-staining outlines. At L5 all the areas have disappeared, and 

 the cord is normal till the second sacral segment is reached, when a peri-central sclerosis 

 gradually enlarges to involve each crescent and extends forwards along each border of the 

 anterior fissure. Areas of sclerosis, limited to the grey matter, also occur in the antero- 

 lateral group of nerve cells on the one side, and in the postero -lateral group on the other. 

 These areas in the grey matter extend for only a short distance in longitudinal extent, and 

 at the fourth sacral segment the only recognisable change is a slight increase in the peri- 

 central sclerosis. 



Medulla Oblongata. — At the level of the decussation of the fillet the appearance of the 

 sections is practically normal, but slightly higher an area of sclerosis, in the middle line 

 anteriorly, gradually increases and forms an elongated oval lying between the two inferior 

 olives (fig. 143). This area involves the mesial and ventral portion of the mesial fillet, and a 

 small part of the pyramidal fibres on both sides. At a higher level this area becomes lozenge- 

 shaped, and the lateral angles pass into the hilum of each inferior olive (fig. 144). As this 

 area is traced upwards it gradually lessens in size, and at the upper level of the medulla other 

 small areas appear, all on the same side : one in the restiform body, one behind, and one in 

 front of the inferior olive : the last of these sends a small process which extends forwards 

 to involve the arcuate nucleus. 



Pons Variolii. — Lower Third. — The roof of the IVth ventricle is extensively involved, 

 the vermis and nodules being completely demyelinated. An irregular area also extends 

 from the one lateral angle of the ventricle and involves Deiters' and Bechterew's nuclei. 

 In the centre of the fibres of the middle cerebellar peduncle on the opposite side, a narrow 

 area is present, and in the same side a large irregularly outlined area extends inwards from 

 the anteso -lateral surface of the pons — involving both pyramidal and middle cerebellar 

 peduncle fibres. On both sides small areas occur, in the white matter of the cerebellum, 

 involving the peduncle of the flocculus. 



Middle of the Pons (fig. 145). — Slight irregularly outlined bands of sclerosis pass round 

 the floor, lateral walls, and roof of the IVth ventricle. Three denser round areas are present 

 between one angle of the ventricle and the lateral surface of the pons : one near the angle, 

 one involving the root-entry zone of the Vth nerve, and one midway between these two 

 points, involving both trapezoid and pontine fibres. Smaller areas are found in the white 

 matter of the cerebellum, especially in relation to the hilum of the dentate nuclei and its 

 outer lamellae. Slightly above this level the peri- ventricular sclerosis becomes more marked, 

 especially at one angle : the area on the pons surface, at the entry zone of the Vth nerve, 

 is increased in size, and several areas occur in the white matter of the cerebellum. 



Upper Pons. — At the lower part of this level the peri-ventricular sclerosis lessens and 



